 Hello and welcome to noon conferences hosted by MRI online. In response to the changes happening around the world right now in the shutting down of in-person events, we have decided to provide free daily noon conferences to all radiologists worldwide. Today we're joined by Dr. Christine Glastonbury. She is a professor of radiology, auto laryngology, head and neck surgery, and radiation ontology. She is a neuro radiologist that academic and clinical interests and head and neck imaging and the vice chair for academic affairs and interim chief of neuro radiology at UCSF. Reminded that there will be time at the end of this hour for a Q&A session. Please use that Q&A feature to ask all of your questions and we'll get to as many as we can before our time is up. We also use the polling feature here at the end so be on the lookout for that. That being said, thank you so much for joining us today, Dr. Glastonbury. I will let you take it from here. Good morning. Thank you so much for joining and I hope you're all doing well and your families are doing well. And boy, this is such a crazy weird time and I have to tell you I think lecturing like this is kind of odd. I realized that when I lecture normally I do a lot of hand waving and things and so now I'm trying to get used to the fact that you can't really see the hand waving anymore. So I'm going to have to get a little more articulate with my lectures, but this is a new lecture I've lectured for a long time on neck nodes and I think it's something that people feel is a stumbling block for them when they're doing neck imaging. So what I'm trying to do is find another way to talk about a lymph nodes in the neck and kind of take on a new perspective. But there are four areas that we are going to talk about during the next 45 minutes. I'm going to go through the nodal levels because I think it's really critical that we speak the same language as our surgeons and oncologists. And they are kind of straightforward once we learn them. So I want you to learn them and use them. I'm going to talk about the characteristics of abnormal lymph nodes in the neck. The things about lymph nodes that should suggest that they are malignant and then how that relates to tumor staging for squamous cell castanoma. And we're going to talk a little about the AJCC and the UICC staging manuals for that. And then finally I'm going to finish with some node pitfalls at the end. And as Ashley said, there are some Q&As. I actually have some multiple choice questions at the end. And then hopefully we still have time that if you have some questions and you want to share what's difficult for you with imaging or specifically with neck nodes, then we'll go to that. Let's start talking about the lymph nodes in the neck. Ruvier was a French embryologist and anatomist and he mapped out the lymph nodes in the neck. And he did this in 1938. He wrote the seminal paper on this and there are around 300 nodes in the neck. And we are not going to go through each and every one of those lymph nodes, believe me. And it is important to know, however, that around 40% of the entire body's lymph nodes are in the neck. So that's an awful lot in a very small space, which I think is another one of the things that makes head and neck feel complicated to people that you've got a lot of anatomy in a very small area. So what we need to be able to do when we talk about lymph nodes is not so much give a count of lymph node number 259, but talk about regions. And so we need to be really super comfortable with nodal levels. So I want to go through a kind of simple system of learning this. We're going to go through examples of this. And I really want you to kind of take this to heart. And really whenever you're reading, neck note scan, start using this. If you do ultrasound, it's a little more difficult because you don't have the same radiological landmarks as you do with cross-sectional imaging. But let's start at the beginning. So level one are all those lymph nodes underneath the mandible. Levels two, three and four are all those nodes down the lateral neck along the jugular vein. Level five is the posterior triangle. So it's behind that sternocleidomastoid muscle. And then level six is the central neck. It's all the lymph nodes below the hyoid bone that are around the trachea and the larynx. So the peri-laryngeal, peritracheal lymph nodes are in the central neck. So that's level six. So that's the basic. One under the mandible, two, three, four along the jugular vein, five down the back of the neck, six centrally below the hyoid. So let's look at each of those in turn so we feel super comfortable with the cross-sectional imaging landmarks. So here's a patient. Imaging is a little higher. This is the U-shaped upside down U, a hyoid bone, which we're going to use as an important landmark. These two parallel, well, kind of oblique digests, muscles are the anterior belly of the digastric muscles. And they're another important landmark for us to distinguish level one A from level one B lymph nodes. So those nodes that are medial to the anterior belly of the digastric muscles are in level one A. And those nodes which are lateral to it are level one B, which means most of the lymph nodes that you're going to see in level one are really going to be level one B nodes. So everything under the mandible, level one, and those medial to the anterior belly of the digastrics are one A. Another important landmark that we're going to use is the posterior margin of the submandibular gland. That's the very back of level one B here. So this margin delineates the posterior aspect of one B. So what sort of tumors will metastasize here? Well, this is the prime location for malignancies arising from the lip and oral cavity, but also those on the cheek and the face and around the eye. So you can see this really big, ugly necrotic node. And if you look on the coronal plane, you can see it's below the mandible. It's lateral to the U shaped here, mylohyoid muscle. So this is a level one B node in this case. And this is secondary to this patient's lip squamous cell carcinoma. This is just a 3D reformat from his CT scan. You can see the primary lesion, but this is a common site for lip and oral cavity tumors to metastasize to. Okay, one under the mandible. 234 are those nodes that are along the jugular vein in the lateral aspect of the neck. Just like this patient here, you can see this string of lymph nodes along the jugular vein, anterior to it, posterior and around the jugular vein. So we're going to separate these jugular chain nodes into three different groups. And we're going to use very clear cross-sectional imaging landmarks. The inferior margin of the hyoid bone is going to separate level two from level three. And you can just see the hyoid on this coronal plane here. And the inferior margin of the cricoid cartilage here is the cricoid cartilage here is going to distinguish level three from level four. And those are your critical landmarks to look for on a CT scan. So all the nodes along the jugular vein are 234 and we're going to separate them by the inferior margin of the hyoid bone and the inferior margin of the cricoid cartilage. So what will metastasize here? Well, level two A, the very top, we're going to start with that. So this is along the jugular vein above the lower aspect of the hyoid. And this is our hyoid in coronal here. And you can see in this case, this big, very heterogeneous, ugly mass. Here is our carotid internal. Here is our jugular kind of pushed up and partly compressed here by this metastatic node. This is the most common site for lymphadenopathy, malignant lymphadenopathy in the head and neck. So oral cavity lesions can also drain back to level two, aropharyngeal and nasopharyngeal malignancies love to spread back to this level. Other malignancies from the nose and the face also drain here. So it's a really common site to see adenopathy. So level two is a critical place to look on every scan. Remember the lower border of level two A is a level two is above the hyoid. So this is one of those examples of the type of really common presentations of we see a certain type of malignancies. This is an MRI scan on and on the left. You can see this very heterogeneous, vocally cystic nodal mass intimately related to the carotid sheet. You can see heterogeneous enhancement of this mass. We're right behind that submandibular gland. Remember the posterior border of the submandibular gland delineates one B from level two. And so this is a level two A lymph node. When you see this, and that is the first thing that you find on the scan, the first place I'm going to look is the aropharynx. And you can see a primary lesion here in the glossotonsular sulcus in this patient. And that is because when patients present with a new nodal mass, first of all, the first thing you're going to think about is this is most likely to be malignant. Any adult with a new neck mass is malignant adenopathy until proven otherwise. The most common primary site for that presentation is in fact the aropharynx. So the palatine tonsils and the lingual tonsil. So it's the first site I'm going to look when I see this. Now that was two A. Two B is a subtle variation of two A. Again, the inferior margin of the hyoid is going to be your delineating level. But two B are those nodes that are near and behind the jugular vein, but not touching the jugular vein. So everything basically in an almost 360 around the jugular vein is a two A. The only nodes that are called two B, which lie in this submuscular recess back here, are those that are behind and not touching the internal jugular vein. Now the reason they're separated, it seems like a little hair splitting here. But the reason they're separated is different tumors like to drain here. And if you look at the list here again, aropharynx, that was in my last list. Nasopharynx also goes to two A. But prurated malignancy and scalp malignancies love to come to this area particularly. So when the adenopathy is just a two B, it may be a pharyngeal primary, but it also should make you think of the possibility of a squamous cell carcinoma that's arisen from the scalp. And it should make you want to look into the parotid gland as well. So let's move a little lower. You can again see here's our jugular vein, our carotid artery. We're below the hyoid and the carotid bifurcation usually in most patients happens around the hyoid bone. So this is common carotid artery here. And I know I'm below the hyoid because I'm seeing part of the piriform sinus here and part of the epiglottis in cross-section. So I'm in the supraglottic larynx. Common carotid jugular vein bilateral lymph adenopathy here. So we are below the hyoid, but we're above the cricoid because the bottom of the cricoid tells me I'm going to be in trachea. So we're still in supraglottic larynx. So this has to be a level three lymph node. This is a common site for, first of all, level two nodes we'll want to drain here, but also pharyngeal tumors and especially hypo-pharyngeal tumors, and particularly the most common hypo-pharyngeal tumor, which is a piriform sinus, squamous cell carcinoma. They love to drain laterally to level three. So this is another patient, jugular vein carotid. Here is the cricoid cartilage, thyroid cartilage. So I'm still in cricoid, so I must be in level three here. And this is one of those super subtle lymph nodes where it is almost completely iso dense to the sternocleidomastoid and the anterior scalene muscles here. The only way you can pick these up sometime is to really make it part of your search pattern to faithfully go down the left neck and the right neck. And there should be nothing behind a jugular vein and nothing between the sternocleidome and this anterior scalene muscle. It should be fat. Obviously adenopathy. Okay, so now we're going to go a little lower and we're going to be below the cricoid. Well, how do I know I'm below the cricoid in cross-section? Well, if you look at the shape of this here, you can see this looks like a horseshoe, an upside-down horseshoe. And you can see this is the esophagus here. So that means this is the trachea. Remember the cricoid cartilage is a bone, excuse me, is a cartilage that goes this way. Now I have tracheal cartilage, which is the upside-down horseshoe, and we have the rounded contour of the esophagus. So I must be below the cricoid cartilage. And behind this jugular vein, between the jugular vein and the anterior scalene muscle, you can see this really large lymph node here. So this is a level four lymph node. And you notice there is lymph adenopathy above it. So when you see nodes at level four, they can have come from level three. It can be from thyroid malignancies, hypopharyngeal tumors. But also, it's important to think of malignancies coming from the chest abdomen and pobus, because we are really in the supraclavicular region. And level four nodes are also supraclavicular lymph nodes. So if this is the only side of adenopathy, this is unlikely to be from a head and neck malignancy up higher. It's either from a hypropharynx, or it's from the thyroid gland here, or a lymphoma, or it's something from the chest abdomen and pobus. And we're going to look at some examples of this. So let's move to level five, which is the posterior triangle. So it's behind the sternocleidomastoid muscle. And in this case, we're going to separate it again. I know let's just split hairs a little, but we do divide into 5A and 5B, because surgical resections can be done just 5A or just 5B. And we're going to use, thankfully, that same imaging landmark, which is the lower aspect of the cricoid cartilage. So on this axiola, I'm actually in vocal cords, because I can see cricoid cartilage here and arytenoid cartilage. When you can see two on the same slice, you're at or just next to the true vocal cords, and here's our thyroid cartilage. So back here in the neck, we're above the bottom of the cricoid. You can see this enlarged lymph node again. Notice how it looks iso dense to the adjacent muscles, which is one of the things that can make it a little trickier on CT sometimes to see lymph adenopathy, because they can look just like muscles. But this is a level 5A metastatic node. So what goes to level 5A? Well, oddly enough, nasopharyngeal tumors can drain back here, but most other pharyngeal tumors do not drain posteriorly. So when a lymph node back here has squamous cell carcinoma, FNA from it, you're going to look at the nasopharynx, but you're going to tell them to look for a skin or scalp malignancy, which has a tendency to drain back here right back in that posterior triangle. And you can see these multiple nodes. It's not a terrifically big node. It is a very FDG avid node here, and these are scalp malignancy metastatic squamous cell carcinoma. That's 5A. Let's move to 5B. So again, we're talking posterior triangle of the neck behind the sternocleid and I'm sorry, but now we're below the cricoid. And I know I'm below because again, the upside down horseshoe here tells me that this is tracheal cartilage. So if we're in tracheal cartilage, we have to be below the cricoid cartilage. And you can see this nodal conglomerate in the supraclavicula fossa in this patient on the right side. One of the landmarks that we're going to use to tell us whether it's here in 5B or here in level 4, which we just talked about, is this imaginary line between the anterior scaling muscle and the lateral aspect of the sternocleidomastoid. So as you kind of may understand in the high end of the neck, the sternocleidomastoid have an angulated appearance. And as they get lower, they kind of come into the coronal plane and flatten out. So this imaginary line separates level 5B from level 4, which is the lower aspect of the jugular chain. But both 4 and 5B are known as supraclavicular nodes as well. Notice this patient has another one hiding over here on the other side, another 5B metastatic node. And these are actually breast carcinoma metastatic nodes. So what other tumors come to 5B? Well, thyroid loves to travel here logically. It's lateral, so level 4 and level 5B with thyroid lymphoma and supraclavicular fossa and anything spreading from above from 5A down. In this case, this is a nasopharyngeal carcinoma with extensive bilateral adenopathy. And on the right, it comes all the way down to 5B and level 4 in this patient. And seeing level 4 or 5B adenopathy is very important for a nasopharyngeal carcinoma staging. Don't forget, however, that supraclavicular nodes, so level 4 or 5B nodes, are also known as vercal nodes. And that means that the metastatic disease can be from the chest abdominal pelvis presenting here. So if the nodal mass is purely supraclavicular, look to the thyroid, then look down south to the chest abdomen and pelvis. Okay, so level 6 is the central neck. So we are below the hyoid now and basically between the common carotid arteries. So here's a common carotid jugular vein, common carotid jugular vein, and you can see this peritracheal soft tissue mass. So the pre-laryngeal, which is also known as adelphian and all the paratracheal nodes are all these central neck nodes or level 6 nodes. It's a really common site for thyroid malignancies as well as larynx and hypopharynx malignancies. But thyroid are the most common and you may be aware of one of the most common neck dissections that's done for a thyroid carcinoma is a central neck dissection where they take out all of those nodes in level 6. So level 7 is not a nodal site of any common occurrence for a squamous cell carcinoma in the head and neck because it's the superior mediastinum and which is below the top of the manubrium all the way down here. And that's because the most common nodes in this area are thyroid, lymphoma, and lung malignancies. So squamous cell carcinoma in level 7 is much more likely to be from a lung malignancy than it is from a head and neck cancer because once they drain down to level 4 and 5, the nodes tend to metastasize to the liver or to the pulmonary parenchyma rather than the superior mediastinal lymph nodes. But it is an important site for staging of thyroid carcinoma and obviously a very common site for lymphoma. So there are some names that I have mentioned a little, but just to also mention that there are many superficial nodal groups, the pre and posterior recular groups, the occipital groups, and facial groups. These are very superficial nodal areas that will drain deep. The jugular digastric is just an old name that we don't use anymore. It's for a level 2A node. Please try and avoid using this. Similarly, try to avoid using Delphian for the pre-laringeal level 6 node. And supraclavicular is a terminology you'll hear a lot. Just get super comfortable that level 4 and level 5B are the supraclavicular nodal groups. So I do want to mention parotid and retrofaryngeal lymph nodes. So the parotid gland is the only salary gland that actually has nodes within it. So when you see a mass in the parotid, it could be a primary parotid malignancy, but it may also represent metastatic nodal disease. And most of the lesions in here really come from the scalp or the face as squamous cell carcinomas or melanomas, basal cell carcinoma doesn't metastaticize to nodes too often. Certain subtypes do like to do that. But most often when you FNA a parotid lesion and it comes back squamous cell carcinoma, it's not a parangeal primary, mucosal primary. It's not from here, it's usually from the skin. And so these are patients, two patients. And honestly, this could look like a primary malignancy of the parotid gland. And there's not much that I can do to differentiate. The patient will get an FNA to make the diagnosis as with all parotid masses. The other nodal group to be very consciously aware of because you need to force yourself to look for these nodes are the retrofaryngeal nodal group. And these are located below the skull base, medial to the internal carotid arteries. So you can see here's a styloid process, super dense, a jugular vein and an internal carotid artery. And this space here is where retrofaryngeal lymph nodes will arise. So on this side, you can see everything's kind of smushed up together and we have this heterogeneous necrotic appearance of metastatic retrofaryngeal lymph nodes. Contrast that with this patient, jugular vein, internal carotid artery, no retrofaryngeal node and internal carotid artery and big right retrofaryngeal lymph node here. So both of these patients have metastatic adenopathy but it is very easy to miss this on CT imaging unless you force yourself to look here. The most common sites that drain here are nasopharyngeal carcinomes. This is the primary nodal station for NPC. Arropharyngeal and posterior wall hyperpharyngeal can drain up and back here. Sina nasal malignancies love to drain here and for some reason known only to the thyroid gland. Thyroid tumors love the retrofaryngeal nodes and if you're doing ultrasound for thyroid you have no hope in seeing these retrofaryngeal nodes but it must be a station you carefully look for if you're doing cross-sectional imaging. Okay, so here's our nodal levels. One, under the mandible. We're going to use the anterior bellies of the digastric. Between that is one A, everything else is one B. Lateral neck, two, three, four along the jugular vein and we're going to separate them by the hyoid bone and the inferior margin of the cricoid cartilage. Level five is the posterior triangle and A and B are going to be separated again by the inferior margin of that cricoid cartilage and then in the midline between the common carotid arteries around the larynx and trachea is the central neck, level six. Okay, so here's my summary of this portion of the talk. Learn the nodal levels. There is no way around it. If it helps, pin up a picture next to your packs, keep it on your laptop or on your pack station, something you can pull up and then use the nodal levels. Try when you're doing it consciously, say this is a level two A nodal mass. This is a level three nodal mass. Once you start thinking like that, you're moving into understanding that certain malignancies in the head and neck like to go to certain lymph node groups and you're getting closer and closer to becoming a really good head and neck radiologist by understanding how these tumors behave and where they drain because it's really important for their management. So before we get to that staging, let's talk about the characteristics of abnormal lymph nodes that's going to make me want to think very, very carefully about whether this is malignant. So the age-old question, does size count? Well, if closet counts, and so big lymph nodes in the neck are abnormal, okay? Now, what is big? Well, I look at them, if they look big, they're abnormal. I don't like measuring lymph nodes. And the reason I say that and I know some people feel really like they need to have a measuring tool to tell them if something is benign and malignant, if you're using a measuring tool, then you've lost the battle here already. So you're going to start by saying, this is bad, okay? And then if you're not sure, it's kind of big, but I'm not really sure, then you're going to look at the internal node morphology because even with the best measuring, you're going to be wrong using size alone up to 20% of the time, which does not go well for the patient. Okay, so these are some of the features you're going to look at when I talk about looking at nodal morphology. And it doesn't matter if you're using CT, it doesn't matter if you're using MR. You can look for these features with both. And in fact, you can look for these features with ultrasound as well. Okay, so round. So this is a retro pharyngeal node and see how rounded this is. And of course, the beauty of multi-detector CT is you get to look at lymph nodes in multiple planes. So round nodes should make you concerned because a normal lymph node in the neck has kind of a jelly bean shape. So once they start getting round like this, you should be thinking this is not normal. These are concerning for metastatic adenopathy. What about heterogeneous nodes? Well, this is a level 2A node, jugular vein is being compressed. If it didn't touch the jugular vein, it would be a 2B. But here is this incredibly heterogeneous lymph node. It's also big. So I would have said this is suspicious, but now I have two criteria to help me. It's big and it is super heterogeneous. This is not a fatty hyalus here. This is a very heterogeneous metastatic node. Similarly, when you look at these, there's a little more enhancement in these clustered nodes. So multiple nodes together is another feature you're going to look at. But when you look at the internal morphology and you see how heterogeneous these are, these are very concerning for metastatic lymph nodes. So cystic change or necrotic change within nodes is really a slam dunk. This is pretty easy. The only thing is to make sure it's not a fatty hyalus you're seeing, but when this is truly cystic and put your household units on if it makes you feel better, then you know that this is a metastatic node until proven otherwise. Another feature we're going to look at is for extra nodal extension, which means that the tumor has not only drained to this node, but now it's spreading beyond the borders of the node. It looks kind of hairy, as I like to call it. And you can see this infiltration into muscle, into the perivascular fat here between the carotid and the jugular vein, and basically into the fat everywhere here. And another patient where you're having a really hard time separating this metastatic nodal disease from adjacent structures, this is suggestive of extra nodal extension of tumor. And this is really an important feature to look for. And there are a couple of imaging guidelines for what suggests extra nodal extension, indistinct margins, irregular enhancement, and infiltration of the muscle or fat around it, which is actually the most sensitive sign of extra nodal extension. And in this big nodal mess here, which is a level two and five kind of joined together as a conglomerate, you can see this is a big, very heterogeneous nodal mess and it's going the whole way through to the dermis in this case. So this is almost coming out through the skin and it's infiltrating the muscle. This is extensive extra nodal extension. Well, we care about that because first of all, it is the most specific imaging sign of malignancy. We're not terrifically sensitive for this, but when you see it, go for it, call it. So let's look at some cases. This is a woman who presents with a left oral cavity squamous cell carcinoma, a carcinoma arising from the buccal mucosa. And so when we look in that case, remember when we started level one is the prime drainage site for oral cavity malignancies. So we're going to look down to one A, one B, nodes under the mandible are level one. And you can see this little nodal conglomerate here and here is our submandibular glands. Remember the posterior margin of the submandibular glands separates one B from level two A. And here is this messy nodal mass. Clearly we have some necrosis. It's very heterogeneous. This is kind of rounded, but it's a little more difficult. Whereas this one with necrosis and extra nodal and there are several together, clustered together. So this should be concerning that these are metastatic. Now, do I know that this one is definitely positive? I feel super confident with this one and I would report this with great confidence. And then I would say there's an additional adjacent node, which is concerning. And here's the thing. It actually doesn't matter in this case whether I think this is malignant or not because all oral cavity tumors will be resected. These nodes will be resected. Both of them turned out to be positive. And on pathology, both of these nodes had extra nodal extension. What about this? This is a woman. She's a heavy tobacco user and she presented with this left neck mass. And you can see this very heterogeneously enhancing. Do I need to measure it? So now it's abnormal. Clearly this is big. This is bad. This is heterogeneously enhancing, but it's also infiltrating the sternocleidomastoid muscle here and the paraspinous muscles here. So there is no question with this one that this looks like it has extra nodal extension, very rounded heterogeneous. And now that I've found that I'm going to look above and below it and indeed there are rounded lymph nodes above and below which are heterogeneous. And these two were metastatic lymph nodes. It does not always matter when you start seeing whether both of these are going to be positive or not by imaging. Once you've found one, you must look for more because it's important for staging. We're going to talk about that in a minute, but these also have the appearance of metastatic nodes. What about this guy presenting with a left neck mass? And you can see here in the lateral neck, jugular vein carotid behind the submandibular gland, we have this cystic mass with a septation. This is not a bronchial cleft cyst. A new neck mass in an adult is carcinoma until proven otherwise. This is cystic necrotic. It's kind of multiple schmush together, fairly sharp margins here. Nothing really looks like extra nodal extension, but this is going to be FNAG because it is likely to represent carcinoma. And in fact, it is a squamous cell carcinoma from the oropharynx. Believe it or not, the primary is somewhere in this palatine tonsil and I cannot even see the primary, but this is proven metastatic squamous cell carcinoma. There are a couple of CT and MR specific signs that can help you as well, particularly with thyroid cancer. So if you see calcification in nodes in the chest, you're going to say, well, this is benign disease. It does not work like that in the head and neck. And that's because sarcoid and all those benign diseases in the chest that give you these calcified nodes don't happen in the neck very commonly. When you see calcification in neck nodes, cancer, okay? Thyroid carcinoma loves to do this. Papillary thyroid, follicular thyroid and medullary thyroid can all show calcifications. Adeno carcinoma, and that's usually something coming from the chest abdomen and pulveris to this level four and level five benodal groups can also show calcification and much less commonly squamous cell carcinoma can calcify as well. Now, MR has another specific sign that should really help you. If you see very heterogeneous nodal masses and you can see the cystic here and maybe some solid stuff as well, a little fluid level here. But on T1, when you see this intrinsic T1 intensity, it may be intrinsic T1 from hemorrhage if somebody has done an FNA, but when you see intrinsic T1, particularly with cystic or heterogeneous nodes in the neck, thyroid is your primary site to hone in on as it was with this gentleman. So yes, size is important, but nodal morphology and the location of nodes with reference to the primary tumor are really important too. And please do not feel that measuring the node is going to answer your question. It's much easier than measuring to actually just look at the internal morphology of that node when you're trying to work out if it's malignant. So let's move on to why this actually matters, and that's for tumor staging for squamous cell carcinoma. So in 2018, the UICC and the AJCC came out with their cancer staging manuals. They do this every seven years or so. And the head and neck groups were ridiculously collaborative in fact so that everything works seamlessly between AJCC and UICC. Prior to these new cancer staging manuals coming out, we had two nodal staging systems for all of head and neck malignancies. You either use the NPC nodal staging if you had a nasopharyngeal carcinoma or everything else used the other. Well, life was clearly way too simple then. We needed to make it more complicated. And in 2018, the AJCC and the UICC introduced this HPV or P16 positive oropharyngeal squamous cell carcinoma staging system. So if you have an oropharyngeal tumor, P16 positive or HPV positive, not the negative ones, only the positive ones, if you have this, you need to use this staging system. Here's the problem. There is both a clinical staging and a pathological. And these two in no way resemble each other. And then the other introduction was a pathology and clinical PN and CN staging system for all other squamous cell carcinomas. So we went from two to five different staging tables. The good news is you don't really need to worry about the pathology tables when it comes to reading the scans. You really just need to be aware that we now have three tables to do clinical nodal staging for the P16 positive HPVs. One for the NPCs, which are usually Epstein bar virus and then all others use this different nodal staging, which is different to what it used to be. So take some screenshots if you need. These are also very easy to look up online. If you just look up the AJCC, you'll find that online. The nasopharyngeal carcinoma, no nodes in zero. It's a lateral node. So nodes on the same side of the neck as the primary and or any retro-pharyngeal, unilateral, bilateral, contralateral, doesn't matter. Retro-pharyngeal end or ipsilateral nodes is N1. If you have bilateral or nodes that are only contralateral to the primary site, that's N2. And if you have a really big nodal mass, and that's not uncommon with NPC to have big nodal masses. So something bigger than six centimeters. Yes, for this, you definitely need to pull out your measuring tape if there is a question of if that's greater than six centimeters because it's going to move it into the N3 group. Or you have nodes below the crycode, which you and I know, that means supra-clavicular nodes in level four or five B are also N3. And the reason this is added in is because if you have supra-clavicular nodes that came all the way from the nasopharynge, there is a high likelihood of distant metastases with this tumor. Now let's compare this unilateral nodes, bilateral or contralateral, nodal mass greater than six centimeters plus this for the new HPV staging. It's a lateral nodes, bilateral or contralode, not lateral nodes, nodal mass greater than six centimeters. It's almost identical to the staging that we already use that is almost unchanged from nasopharyngeal carcinoma. So there is no N3 if you have supra-clavicular nodes with P16 positive HPV squamous cell carcinomas of the oropharynx. But you can see otherwise this looks very similar. So it should be a little easier to remember. Now for the P16 negatives, HPV negative oropharyngeal tumors and all other head and neck tumors that are not nasopharyngeal, there is this somewhat more complicated nodal system to remember. And this actually up to the N3 is completely unchanged because it used to be in 2017 and prior. It was one node is N1, more than one node is going to be N2. Or if it's a really big node, more than three centimeters, again, call your ruler out for this one, have at it. Bilateral or contralodes, N2. If you have a really large nodal mass greater than six centimeters, okay, remember that's just the same as NPC and P16 positive, greater than six centimeters is always bad in the head and neck. Then it's going to be N3 disease or the entity that we were just talking about of extra nodal extension. So this is the addition that happened to this area, but it is, you'll notice the little C here. That means by clinical exam, not by radiological exam, but by clinical exam. So we talked about the imaging features here of extra nodal extension. Clinical extra nodal extension is described as very clear description in AJCC and UICC, and it is really a physical exam finding. Now, when I see this, you bet I'm going to say there are imaging features of extra nodal extension. And if they can't feel this, you need to get the patient another doctor, but this is a fixed mass. There is clearly infiltration of the musculature on imaging, but at the moment, C-E-N-E, which makes metastatic disease N3, the worst it can be, needs to be a clinical exam finding, but I absolutely direct my clinician to what I can see on imaging. So the summary of this section, know your primary, pull out the staging tables. It makes it so much easier to know what you need to look for. And you have my blessing to measure nodes to determine if they're over three centimeters, when it matters, or over six centimeters, which matters for all head and neck malignant seas. Okay, I'm going to finish with a couple of node pitfalls. Where we go wrong in this, and what we kind of, like, I think radiologists do way better than they think they're doing with lymph nodes, but there are two big areas where I see the misses happening. Number one pitfall is somebody missed the nodes. They just didn't see the node, or if they did see it, they certainly didn't report it. And number two is they didn't think of a differential diagnosis. And that's because nodes are not always squamous cell carcinoma. They're not always from the head and neck. And what looks like a node is not always a node. So let's look at that. So that first thing that people just missed the nodes. So there's a lot of nodes. As I said, there are 300 nodes in the neck, and we're not here to report every single one of the nodes. But what we are going to do is develop a really consistent method of looking at lymph nodes. So what I'd recommend you do, and I do this, obviously, I look multi-planar, but before I finish a dictation, I'll go down the right neck, the left neck, retropharyngeal, right left retropharyngeal. And you need to develop a pattern. So you're forcing yourself to look for lymphadenopathy. Once you start to get used to the patterns of how head and neck tumors like to metastasize, for example, I mentioned thyroid does this crazy thing of going up to the retropharynge. You're going to remind yourself every time you read a thyroid, I've got to look at those RPMs. Or you can just develop a system right, left, retropharyngeal in every single patient. Okay, what about the type two errors, the ones where it was something else? Well, this is a gentleman who presents with a right neck mass, and you can see we're at the cricoid here. So we're at the bottom of level three, coming down into the supraglibular fossa. And you can see bottom of level three, and you can see bottom of level five A here. There's multiple nodes clustered together. They're big. I don't need to measure them. They're abnormal. And PET makes this really easy by showing you extensive FDG uptake. This was FNAID, and this is adenoic carcinoma. Whenever you see nodes just starting down here, it can be from the pharynx. Although not often will you see adenoic carcinoma come from the pharynx. Most pharyngeal tumors are squamous cell, and more than 90% of head and neck tumors are squamous cell. So when you just see nodes starting down here, don't forget these are the site of metastatic nodes from the chest, abdomen, and pelvis. And in this case, this is an esophageal primary tumor, pretty subtle on the cross-sectional imaging. But this is metastasizing to the supraglibular fossa. So vercal nodes. And you know that we normally think of them left. They can be right-sided too. It doesn't matter. This is a woman had a left neck mass. And these are really crummy images. And you should know that whenever a radiologist shows you a case with really crummy images, that's because that's all they had, but it's such an interesting case. They wanted to share it anyway. So this is a PET CT, and it's my least favorite type of PET CTs. And those are done without any intravenous contrast. And I guarantee you if contrast was given in this case, this error would not have been made. So this patient presented with a left neck mass. A PET CT was done without contrast. And you can see really super intense FDG uptake. This must be malignant, right? And I can't tell you anything about this. I can't tell you if it's going to be easy to resect, if it's going to be involving the crotted, if there's extra nodal extension. I can't tell you anything at all. They didn't see a primary site anywhere on the PET CT, which was the reason for the PET CT. And that's all they had before they opened and did an incisional biopsy, which by the way, incisional biopsies are never a good idea, but that's for another day. Well, this turned out to be a paraganglioma. This is not a nodal disease at all. And perhaps if contrast has been given, the extensive hypervascular nature of the mass would have been made clearly evident. They did not have fun in the surgery and they were not happy about this. And I was like, well, I couldn't have predicted that. So there you go. This is one that Jen Hong shared with me. This is a woman presenting with a cystic right neck mass. And this one just destroys every argument I have about lymph nodes. But I think it's definitely worth sharing anyway, because as we said these, it's the exceptions that make the rule called true. So she presents with a right nodal mass. Here's the hyoid. So we're at the bottom of level two, submandibular gland, jugular vein, common carotid artery here, very cystic on T2-weighted images, very heterogeneous, ugly enhancement of its medial portion, but very sharply circumscribed. And here's the same ultrasound that was used so that she could have an FNA, which showed spindle cells. So you don't have spindle cells in squamous cell, carcinoma is all thyroid, carcinoma is in fact, this was resected and this is a schwannoma. So my adage that I will tell you over and over again is that a new neck mass in an adult is cancer until proven otherwise. And then Jen gives you a case that it's not. There's nothing I can do to argue with that one. This is a schwannoma, a very, very cystic schwannoma in the neck. So new neck mass in the adult is carcinoma into proven otherwise. Always look for a primary site and consider a differential diagnosis, but given whatever imaging modality you have. So that's kind of my 45 minutes of what I wanted to share. My take home points are really that I want you to really learn and then use the nodal levels. Really have a chart up if you need and it doesn't take long to get really comfortable. One under the mandible, two, three, four down the lateral neck, five in the posterior triangle, six are central. Easy. Look at the nodal morphology. Size of the loin is not the answer. If they're really big, then piece of cake. But when they're not really big, don't measure them. Look at the morphology instead. Pull out the staging tables. You can see they're kind of similar to each other. There are easy things to remember to remember with that. Anything six centimeters or above, you know, as an M3 node, no matter which staging table you're looking at. And then really develop a strategy for reviewing left nodes. So mine is left, right, retro farangil. Whatever works for you, just use it. And just remember that there are some tricks and there are some pitfalls, but overall head and neck squamous cell carcinoma, nodal imaging should be fairly straightforward once you get comfortable with each of those four items. Okay. We have some time definitely for questions, but before we get to the questions, I have some questions for you. So I think if Ashley's here, I'm going to ask her if she can share. Ashley, can you share? Oh, fantastic. Brilliant. Thank you so much. So we've got the polls. So you'll see on the bottom or on the top of my screen, you'll see where it says polls and you can answer your questions through this. So feel free to have out at the good news is I have no idea who says what. When I've done visiting professor before, I did it recently with Wisconsin. People were all answering on the chat function. I had no idea, but just answer on the poll function. Okay. So let's start with the first one. I got four of these. What level are we going to call a lymph node? That is enter a lateral to the left. So it's anterior to the posterior margin, the subman, and it's lateral to the supplement of your plan. Is it one a one B to a or to be. So you got four choices. So I'm just going to give you a few moments. Okay. So we're totally rocking this. I would like to think it was because of my teaching. I think it's just because you're rocking this. Excellent. That is correct. So a node, enter lateral is to the left. Some interview plan is one B. So remember everything under the mandible is one. A is between the anterior bellies. B's are the rest. And they're always anterior to the posterior margin of the some individual plan. Terrific. Oh, can we go to poll to question please? Okay. This is quest. Oh, no, I see it comes up as one again. That's kind of cool. Okay. So nodes that are adjacent to the jugular vein. So they're adjacent to the jugular vein. Below the hyoid bone. And lateral to the larynx. A which level. So they're adjacent to the jugular vein. Below the hyoid. And lateral to the larynx. So that's a kind of a clue. If I'm saying lateral to the larynx. Then I'm telling you it's above the bottom of the cry. Coid because the bottom of the cry. Coid is where the larynx ends. And we start cervical trachea and cervical esophagus. Big transition point. Okay. Level three and level three is correct. Really good here. By the way, that is insane. That is the same percentage. 81%. For question one and question two. Okay. So let's move on to the next question then. And enlarged and necrotic node at level one B, which may or may not be correct. And enlarged and necrotic node at level one B, which may or may not be an exact image that I showed you. Is most likely to have metastasized from a primary mucosal tumor. In which site? Oral cavity or a pharynx, hyper pharynx or nasopharynx. That's a lot of pharynx. So let's see how we're doing with this one. I think I have one more question up to this. Terrific. Oral cavity. And this is probably a fairly basic question to answer. There are long problems for it, but it's really important to come on good topics for this meeting. Fran, is there a few things to keep in mind when we hear about or what are some problems with falls? Some of those concerns I've heard a lot on, well, of small area gboarding that we're talking about right. You could even try to, I think I think, how to turn it over here. So continue with your places ahead and recognize the pain. So that is straight to it. it is most likely to have come from the oral cavity. Okay, I think I have one more, Ashley, if that's correct. Terrific. Okay, what is the most specific sign of malignant involvement of a node? That it's big, that there's extra nodal spread, that it has a rounded contour, or that it's calcified? I think I actually used exactly this term. Big, extra nodal extension, rounded contour, or calcification. So as you guessed, each of those are things you're looking for. Excellent, the most specific sign is extra nodal spread. All of these features are features that make me concerned for malignancy and make me triple look at the node, but this is the most specific sign of malignancy. Okay, so I am going to now go to the, I think it works best if I go to the QA to answer this question. Does that work, Ashley? Yeah, that's perfect, and I'll follow along and kind of click on so people can see which ones are being answered. Terrific, okay, so I've just gone to the top of my list if that works, and I send a question. So the level one B lesion you showed looked like an abscess, how would you, excellent question. Oh, brilliant, gosh, and I can tell you, I'm just working on a project of this with one of my fellows at the moment. So it does, when you see cystic lesions, they do kind of look like abscesses. However, when you look at that lesion and when you look at necrotic nodes elsewhere in the neck, you'll notice there is no infiltration of the fat around it. So any time you stick a little bag of pus somewhere in the neck as an abscess, it's going to incite a lot of inflammatory change around it. So the absence of inflammatory change is the critical thing here to tell you this is not an abscess. Now, most of the time the clinician knows too, but that is the most helpful thing for me for imaging. One of the problem areas can be when you have big metastatic nodal mass and the classic is a patient with scalp carcinoma that drains down to level five, the posterior neck. And these often present and they can have huge nodal masses. I'm talking six centimeters easily. They can have an inflammatory reaction with it and always head for malignancy first. But if there is no inflammatory change around that necrotic lesion choice, then that should be the key that this is most likely malignancy and not an abscess. Okay, I hope that helps. Do you put the TNM classification? Okay, great question, Oscar, brilliant question. So it depends. Sometimes I put that question into it, I put that answer in there. There are areas where the radiology cannot because part of, for example, oral cavity malignancies, the T in an oral cavity malignancy requires pathology because you have to know the depth of invasion below the basement membrane. And MR and CT are good, but I ain't that good. So you cannot do a TNM for oral cavity. Strictly speaking, by the wording in the AJCC and the UICC, you're not supposed to, only to avoid confusion in patient care and patient management, only one person is supposed to assign a TNM for that patient and that person is supposed to be the managing oncologist or surgeon. So I don't, but what I do think is really important and I've written several pieces about this, so I don't know, Oscar, you're just asking the right questions here for me, but I think it is really important that you have the staging tables out so you know what to put in there so that the oncologists can answer the questions they need to answer and can do the staging. So I think that bit is critical. I don't think it's critical if you choose to do it and that works for your surgeons, great. Remembering that there are areas where you're going to be wrong and that's not good and I don't wanna make confusion for someone taking care of my patients, excuse me, someone taking care of their patients that I'm participating in, but I do wanna make sure all the important criteria are in there and sometimes I will say something like, there is clear intracranial extension which would make this a T4 tumor. So I will use something like that. Okay, I hope that helps. Okay, I'm gonna go down to the next one, Parash. How to differentiate level 2B from 5A? That is such a great question. So level 2B actually has a name that the surgeons have used for years, years before we had a level system when we talked about triangles in the neck, muscular triangles, and it's not as the submuscular research because it's underneath that sternocleidomastoid muscle. So deep to the sternocleidomastoid muscle is strictly speaking a 2B, behind it is a 5A higher in the neck. It's easier as you get lower in the neck. I don't measure long or short axis. The only time I measure is the next question, sorry. The only time I measure is to tell if something is more than three centimeters or more than six centimeters and as with all other measurements that you should do for AJCC or UICC it is always looking at the longest axis of the lesion in the neck, okay? Always looking in longest axis. Okay, how to differ, Parash had another really good question. How do you differentiate four from superclavicular? No, no, level four is a superclavicular node. Level four and 5B are both superclavicular nodes. So when the clinician says there's superclavicular adenopathy, it may be four, it may be 5B or it may be both, okay? Does that make sense? Why not MRI greater than CT for nodes all the time? Well, so that, Herman, this is a great question. So I think MR, people don't like MR in the neck and we'll talk about that in two seconds. I think MR is way better for retroferential lymph nodes and for seeing those little subtle nodes in level three and four particularly, which hide behind the sternocleidomastoid or behind that jugular vein that look iso dense to muscle. It's so easy to miss those nodes on CT and that's why having a system of how you look at nodes is really critical to me because it's just too easy to look straight past them. Everybody's done it, I've done that. And you just look at them after like, how did I miss that? Well, because they're iso dense to muscle. So MR is much easier. The problem with MRI is obviously multifold. People tend to do MRI with enormous field of view, non-focused MRI that now gives you at least three sequences, T1, T2 and GAB, in at least two planes. So you have a whole lot of stuff to look at and it kind of feels harder and the patient's much more likely to be moving with an MRI. So the potential to get a consistently readable study with MR is much lower than the potential for a consistently readable non-motion degraded CT. So I would definitely, you know, you have to read CT. It's what we do kind of most of in most places. I think MR is a little easier for looking for lymph nodes but that's that one thing with a caveat that people reading, doing MR all the time will know that patients like to swallow and move and it's difficult to do it well. Okay, Maurice has a really good question here. Can a pathological lymph node from squamous cell carcinoma be completely cystic, like with a completely regular thin rim or the rim has to be irregular? No, it can look like a perfectly neat cyst and that's why they get mistaken for brinkill cleft cyst because there's no thickness to it and the additional problem with that, Maurice, with those is that if you do a PET CT in these because there's not enough tumor there to take up FDG there can be zero FDG uptake and those reports make me wanna cry when it says there is no uptake in association with this therefore this is a brinkill cleft cyst. You know what, nobody ever died of a brinkill cleft cyst so always go for this must be aspirated since it may represent metastatic squamous cell carcinoma. And by the way, thyroid cancer can do exactly the same thing, metastatic thyroid can give you a completely neat and tidy cyst with no thickness or no chunkiness with it. Okay, Hammond, how do you personally rate or use short axis size? Yeah, I don't. As I said, I don't measure nodes except to say if it's above three or six centimeters because it's going to change the nodal staging and then you always use long axis. Now, most metastatic nodes are kind of roundish anyway until they get really big and so the short axis and the long axis are pretty much the same anyway. Okay, can you anonymous attendee? Can you tell something about post radiotherapy CT imaging of nodes? What are the imaging features suggestive of residual tumor? Brilliant question. And gosh, I wish we had the answer for this. So post treatment imaging is a whole separate section that's really important and really difficult if you're doing this. And I, you know, you have my sympathy with this as well. So first of all, when you're reading the post treatment scan you want to have the pretreatment, you want to know where the primary disease was not just the primary malignancy but where the initial nodal disease was that you're looking and you will obviously want to see it decrease significantly over time unless I have a very small residual nodal disease left I am going to say this is concerning for ongoing residual disease. And then we do pet. That is our routine here. You could go straight to ultrasound from that point and take a look and or FNA them as well. There are a percentage and gosh, I wish I had it on the top of my head, the actual percentage of post treatment nodes which are still large. They're still, you know, 15 millimeters or so in size which is big and they can look concerning. You do a pet and they may even be positive on pet. And then when they resect those nodes which is the standard treatment for residual tumor after treatment, if you want the patient to live you got to do salvage therapy at that point. And if they do resect, you'll often find that there is no viable tumor left. So it is difficult. So anything if that nodal mass has not gone down to below 15 millimeters or more roughly, again, I'm not measuring, then these patients will go on to get a pet in our shop and that's how we manage them. And in other shops, I imagine that they will do ultrasound evaluation but you're looking for that. So eight week baseline scan, I expect to see no residual primary tumor and I do not want to see any residual adenopathy. If there's anything suspicious that patient is now going on to get a three month pet. If it is clearly progressed, then now we're moving on to something else. Okay, Teresa has a question here. I'm going to keep going Ashley until you tell me that we're done and we're out of here. Perfect, I think about 10 more minutes would be awesome. Terrific, okay. So when performing staging and we come across a conglomerate of multiple nodes, how should we measure the biggest node of the multiple nodes or consider the conglomerate as a whole? Excellent question, Teresa. And that's the, I love this sort of question because this is the, okay, it's all great to have this theory but how do I actually do this stuff when I'm reading scans? So I describe that as a nodal mass and if I really cannot distinguish separate nodes from that, then I measure the longest diameter of that nodal mass. If it looks like I showed you an extra nodal extension with a node above and below, they clearly look like separate nodes in that situation. But when they're all mushed in together and it's a nodal conglomerate, I will describe that as a nodal conglomerate but they really have to look like they're stuck together. Otherwise, if they're just sitting next to each other, no, then you're measuring the actual biggest of that. Marla, how to differentiate a metastatic node from an effective node? Excellent question. And again, often the clinician knows infection way before you do because they've had a look. But in this case, when you're, I kind of answered this a little at the beginning, look for inflammatory change around it. And if in doubt, if you see one's a little inflammatory, just think about that. If you put a bag of pus in the neck, you're gonna get inside a whole lot of inflammatory reactions. So if you're not seeing a lot of inflammatory reaction, this is gonna be a cystic or necrotic node. And by the way, it doesn't matter if something is cystic or necrotic, same thing. Malignancy, malignancy, okay? We tend to think of cystic nodes as having a thinner rim and necrotic nodes as being very heterogeneous internal contents, which is easier to see on MR than it is on CT and a thicker margin. Okay, anonymous attendee, how to differentiate 2A from 2B? Okay, okay, so remember lateral neck 234 and level two of those nodes that are above the bottom end of the hyoid. So 2A are the nodes medial, lateral, anterior to the jugular vein or posterior and touching the jugular vein. 2B are those nodes further back so they're behind the jugular vein and not touching the jugular vein, okay? Excellent, another anonymous attendee, does it help that maintain fatty hyalum of the lymph node to differentiate from malignant to non-malignant? Absolutely, and in fact, if you're doing ultrasound of lymph nodes, that's what you're usually looking for. You're usually looking to see that there is loss of that fatty hyalum, often increased flow in the node as well as a heterogeneous appearance. So yeah, loss of the fatty hyalum and if you see a preserved fatty hyalum, you can feel pretty confident that that is unlikely to be a metastatic node. Okay, professor, a level 1A, this is from Sujitra. Thank you for sending a question. Level 1A, does it have a right side or a left side? No, level 1A, a midline. So they're between the anterior belly so that they're gastric below the mandible. So that's level 1A. All the other nodes in level 1A, level 1B, but it's a midline part of the subendibular area. Okay, superior from Solgata, superior margin of level 2. How does it relate to the high retroferential nodes at the skull base? Well, the retroferential nodes are the retroferential nodes. So they are medial to the internal crotted arteries below the skull base. And you have medial ones there, a lateral one's there, and a little low, you'll see medial lymph nodes here. But these are all, the level 2 and the retroferential are really quite distinct from each other anatomically. Solgata, I'm not answering this question very well. I think I'm not sure I completely get where you're going with this one. If you wanna type something else in, I'll see if I can get to that too, to give you better clarity of what that is. Okay, I'm going down. I see some more short axis, long axis. Please never measure a short axis. I don't know what that is supposed to help anybody with. A 2B versus 5, I mentioned, ah, awesome. Do we look for level 7 in thyroid carcinoma? Well, you should absolutely. When level 7, those are the superior midi-stinal nodes. So they're below the top of the manubrium. This is, these are not something you can see with ultrasound, but if you are doing a CT or an MR of the neck and someone who has what you think is thyroid malignancy or if you ever see lymph nodes at level 6, just take a look down to level 7 on your CT. And it's one of the reasons we like to do all our neck CTs down to the aortic arch because that covers level 7 as well in that. So I do wanna cover that, but no, you're not gonna see that ultrasound. You're not gonna see level 7 with ultrasound and you're not gonna see retrofaryngeal nodes which are important for thyroid cancer with ultrasound either. Okay, so got another great question here. No use of radia for extra capsular extension. It's actually, we're supposed to call extra nodal extension, E-N-E. Why don't we use this? Well, the reason we don't use it is because we are not very sensitive to it. And this makes this nodal staging in three. So it turns out you have a, gosh, see this is why I wanna be in a room. I wanna like wave my arms around when I'm explaining this. And one end of the spectrum, you have clinical exam which is not terribly sensitive but pretty specific for extra nodal extension but terribly sensitive. You know, we're talking way, way low sensitivity. The other end of the spectrum, you have pathology for extra nodal extension which is pretty sensitive and specific. Well, I mean, essentially it's your gold standard. So I guess you start with that anyway. And then you have radiology. It is definitely more sensitive than physical exam. It's very specific. With you see it, you should feel pretty confident it's gonna be there. But the problem is where it is on that spectrum. And to me, this is not so much an imaging problem. It's an interpretation problem. And this is the kind of thing people don't talk about in studies. People talk about, oh, CT is so sensitive for this or MR is, it's not really the CT scanner that is or MR scanner is. It's because we're all human and this is really, really hard stuff to do. And it's really hard to interpret things sometimes. So we're not very sensitive for it. And if you look at all the papers that have been done on the radiology sensitivity and specificity, specificity for extra nodal extension, they're all over the shop with how good we are at it. So that's why, because the implications for calling it means M3B disease. So you're now talking stage four for most patients. That's pretty savage. So they just didn't think radiology was there yet in order to make it part of that. But believe me, if I see it, I'm calling it that there are imaging features suggestive of extra nodal extension. But as to the question asked before that I would not say this is therefore M3B because you cannot designate M3 without a M3B on the basis of extra nodal extension without a clinical exam. Okay. Diffusion weighted images and nodes. What are your thoughts? I love the anonymous attendees' questions. I have many thoughts. I love diffusion weighted images. Here's the problem, overlap. I mean, you're talking about the biggest overlap, Venn diagram ever basically of positive and negative nodes. I think we were all thinking that when diffusion came on board it would be the answer for nodes. It's almost never the answer for lymph nodes. And that's because you have such great other information already. You've got morphology to look at. And if the node is what we really wanted with diffusion or frankly any magic wand with imaging is not to be able to see the two centimeter node or the clearly necrotic cystic node like no kidding. I already know that that's malignant. You want us to help us with the sub-millimeter, sub-centimeter metastasis. So the nodes that come out that are three to four millimeters of metastatic disease with them. That's what we need from imaging that we don't have yet. And diffusion is not going to do that because as you well know, diffusion has the crappiest excuse my language has really bad spatial resolution. So diffusion is not the answer. Like knock yourself out if you think it's helping you with things but generally I don't find that it really solves the problem which is for the small nodes that are otherwise indeterminate to me. So I don't think it's super helpful. I wish it was. I wish there was an answer to this. Okay. I think we have to answer about one more question. Okay. So an anonymous attendee. How can you different? Oh, I just, it just disappeared. Isn't that weird? Oh, here it is. The Burkow node is between the thoracic duct and left supraclavicular vein. Therefore it's in the left supra, ha ha. Yeah it is, but guess what? It can also be in the right side as well. So if you look at the anatomy literature and there's actually a really nice paper by Charbrandt Stetter looking at alimphatic malformations in the supraclavicular fossa, you'll see that anatomically it can be left and right thoracic duct or it can be a right thoracic duct or it can be left and that's why you can have either side metastatic nodes. So it's not this neat and tidy. The body is never totally neat and tidy. There's all sorts of exceptions of the alimphatic and it does not always just go to the left. Okay, Ashley, I think I've exhausted everybody. Perfect, as it brings to a close, I want to thank you Dr. Thassenberry for your time today. We really appreciate it. And thanks all of you for participating in this new conference or a reminder that it will be made available on demand on MRIonline.com, complimentary in addition to all previous new conferences. And tomorrow please join us for a new conference with Dr. Mark Goslin on acute care imaging, what's not in the books. You can register for that all upcoming at MRIonline.com. Thank you and have a wonderful day. Thanks so much, Ashley. And thank you all for listening in and email me, ask me questions. Take care and stay well.