 We're going to start with a few simple items of anatomy and then talk about the approach to imaging of the nasopharynx, but I really want to concentrate on nasopharyngeal carcinoma because this is the major area of pathology that we'll encounter in the nasopharynx. We'll talk about both primary nasopharyngeal carcinomas and about how we stage the nodal disease, and we'll briefly talk about some of the differences between the old AGCC7 and the new AGCC8, which was introduced just last year, so we're still getting used to the new staging system. So beginning with some anatomy. When we see an axial image in the nasopharynx, the thing that is bulging out into the nasopharynx there is the torus tuberius. This is a cartilaginous cap that props open that opening of the eustachian tube. Now just lateral to that is the opening of the eustachian tube that the torus tuberius is keeping open. But if we go to the other side of the torus tuberius, what we have here, you can see the enhancing mucosa line that comes around the back of the torus and then around the dorsal aspect of the nasopharynx. This is a potential space, there's nothing in there except those two layers of mucosa coming in, turning around, coming back out again. This is the fossa of Rosenmühler and it is a very important anatomic region because it is the most frequent site for nasopharyngeal carcinomas to arise. Now these two black lines that are running vertically here, those two black lines are the tergoid plates. They are bony structures arising off the back of the maxillary sinus and there's a medial and lateral tergoid plate onto which the medial and lateral tergoid muscles anchor. These muscles here are called the prevertebral muscles. Now you might think that these are longus coli muscles which through most of the neck occupy this position, but when we're so high up near the skull base, it's actually the cousin, the longus capitis muscle that is the majority of this muscle bulk, a little bit of longus coli there, but mostly longus capitis muscle. We'll just call these the prevertebral muscles. If we go out laterally, now we're in that carotid space where we have the carotid artery, the internal regular vein, and associated nerve structures. These three arrows are supposed to point out the bony structure that is along the back of the nasopharynx. This is of course the clivus which separates the nasopharynx from the intracranial vault. Looking a little bit lower down, we are seeing the paraffaryngeal fat out laterally. Very important structure for us to recognize and very important anatomic relationships, just anterior to that are the medial and lateral pterogoid muscles. So that's sort of the anatomy that we're going to be referencing as we talk about nasopharyngeal carcinoma. So nasopharyngeal carcinoma is a disease endemic to East Asia where there is always the non-charitonizing, undifferentiated form of squamous cell carcinoma. It is associated with Epstein-Barr virus infection. Nasopharyngeal carcinoma is treated non-surgically with chemo-radiation unless debulking is needed for extremely large tumors. An MRI is the preferred modality for staging primary nasopharyngeal carcinoma. We want to use MRI. Sometimes we end up with a CT, usually in situations where the diagnosis is not established yet, we don't know what we're dealing with nasopharyngeal carcinoma. Or in patients, of course, who are unable to undergo MRI, we use CT as our fallback. Well, PET CT is not necessarily useful for imaging of the primary tumor, and the CT and MRI will do an adequate job for the nodal disease. But if we are interested in whether or not the patient has distant disease, that's where PET CT really shines. So we're going to only use PET CT in situations where there is a high chance for distant disease. And what are those situations? Well, if the patient has a very large primary tumor, a T3 or T4 primary tumor, which we'll talk about in a moment, if the patient has advanced nodal disease, and by advanced here we mean any nodal disease. So even N1 disease in the neck predisposes the patient to distant disease. And if there are clinical signs of distant disease, for example, liver enzyme elevation suggesting hepatic metastases, then we think that PET CT is worthwhile to detect that distant disease. Now, if you happen to have a PET MR scanner, you can combine this into one examination for the patient. You can get the MRI of the skull base and a full body MRI combined with the PET. It's a very useful one-stop shopping for the patient. You've found this to be a very useful tool, PET MRI. Let's talk about how we categorize primary tumors in nasopharyngeal carcinoma. So a T0 is no primary tumor identified. A T1 is disease confined to the nasopharynx. It's in the nasopharynx. We allow for the oropharynx. We allow for the nasal cavity, but it is confined essentially to these mucosal spaces. T2 disease is disease that has extended to the paraffaryngeal spaces. By that I mean the pterygoid or prevertebral muscles, the paraffaryngeal fat, or the carotid space. Those are considered paraffaryngeal spaces. T3 disease is where we start to involve the bone. Those are the bones of the skull base, the bones of the spine, the bones of the perinatal sinuses, or those pterygoid plates that we were discussing. To get to T4 you need to involve distant soft tissues, by which we mean intracranial vaults, any spread along the cranial nerves, into the parotid gland, into the orbits, and into the hypoferyx. Those are all T4 lesions. Let's show some examples. We'll start, of course, with T1 disease. And here we see enhancing tumor, and it's filling out the fossa of rosin mule, thickening it up and extending across midline, uniformly enhancing. But all of the surrounding anatomy is preserved. We can still see the torus, and this is disease confined to the nasopharynx, a classic T1 appearance. You can also evaluate this well on unenhanced imaging. Note the preservation of the surrounding fat planes here. That's really important for convincing us that we're only dealing with T1 disease. Another example of T1 disease confined to the nasopharynx. Note this small line, this thin line of fat in front of the pre-verteral muscles. That's a really important clue. If that fat line is intact, that tells us that there's been no posterior spread into the pre-verteral musculature, very reassuring sign. How about this case? This looks a lot like the ones that we've just been showing on a sun-enhanced scan. There's a little bit of filling out, but is this confined to the nasopharynx? Well, if we look at our T2 weighted images, we're going to see that there's a deema throughout this pre-verteral musculature, and that's an indicator that it's been eroded. And now we have extension to the pre-verteral musculature that defines this as T2 disease. Well, once again, we might say, well, this looks like it is well confined. But look carefully, and you can see that the pre-verteral musculature is involved in this examination. Notice how it is preserved on this side, but violated on that side. That asymmetry is our clue, that we have invasion of the pre-verteral musculature. This is T2 disease. How about here? What is our extension that defines this as T2? Now we have extension out laterally and posteriorly. Notice how the internal carotid artery is completely surrounded by that infiltrative tumor. This is T2 disease because of involvement of the carotid space. What do we need to invade to make it a T3? Well, here's an example where we have invaded posteriorly. Certainly pre-verteral muscles are involved, but it goes even further back. Here we are involving the clivus that is one of the bones that renders us T3. Are there other bones that can be affected? Yes, absolutely. Look at this situation where we see abnormal enhancement and invasion as this tumor comes back to involve the occipital condyles and the lateral mass and transverse process of C1 spinal involvement. Another bone that renders our primary tumor T3. So what does it take to become T4? Now we have to get into those surrounding soft tissues. Here is an extensive tumor completely surrounding the internal carotid arteries, involvement of the middle cranial fossa. Extension through and through the clivus. We're not just in the bone, we're through it. Now we're in the intracranial vault, displacing the basilar artery, extensive involvement T4 disease. If there is perineural spread, we're going to call that T4 disease. Here's an example coming back along V2. That spread of disease is going to render this a T4 lesion. Here's another example, extensive dural spread and involvement of the intracranial structures. Again, T4 lesion. If it comes so far forward that we have extended through the bones of the perinatal sinus, but here is one of the most important things. Look how this has spread out laterally to involve the masticator space. Once you get out into the masticator space, T4 disease from this rather extensive tumor. Okay, let's move away from the primary tumor now and talk about how we classify nodes in nasopharyngeal carcinoma. It's a little different from most of the scrimaceous cell carcinoma that we encounter in our neck, so it's worth discussing specifically. N0, no surprise, no nodal diseases, N0. N1 disease is unilateral disease. Okay, doesn't matter how many nodes, unilateral disease. But retrofaryngeal nodes are special. Retrofaryngeal nodes are so frequently involved by nasopharyngeal carcinoma that you can have contralateral retrofaryngeal nodes and it still counts as N1. N2 is bilateral disease, not including the retrofaryngeal nodes, bilateral nodes bilaterally. To become N3, there's two ways you can be N3. You can be greater than six centimeters, a single nodal cluster that is greater than six centimeters, or you can extend down below the inferior margin of the cricoid cartilage. If you're that low down in the neck, that also renders you N3 disease. So here's a classic example of N1 disease on a PET CT. There are multiple nodes out here, but that doesn't bother us. It's still N1 disease because it's unilateral. Here's a good example of retrofaryngeal node on PET CT. This is its location, medial to the carotids. It doesn't matter what side the primary is on here. It's still going to be N1 disease. What if we have bilateral retrofaryngeal adenopathy? Okay, bilateral retrofaryngeal adenopathy, still N1 disease, right? We allow for bilateral retrofaryngeal disease. But once you get bilateral disease out into the lateral chains, now we've escalated, we're up into N2 disease because we have bilateral involvement. This is in level four within the neck. We're below the level of the trichocryl carotid jaw. We see here is thyroid cartilage. The larynx is above us. Now we're low enough to call this N3 disease. I want to make a specific note about unknown primary tumors to talk about that T0 we referred to earlier. What's an unknown primary tumor? This is when we identify squamous cell carcinoma in a lymph node as a neck mass. Now we know that squamous cell carcinoma doesn't arise in lymph nodes, so it had to come from this mucosa somewhere. But we don't know where it came from. And we do a clinical examination, we do panendoscopy, we do a CT scan. We cannot find the primary tumor anywhere. Now we call this an unknown primary tumor. So how do we take an unknown primary tumor and say this is really a type of nasopharyngeal carcinoma? We look at the viral status of the node. If that nodal sample is positive for Epstein-Barr virus, we are going to assume that the primary tumor must have come from the nasopharynx. So this is how you end up with a T0 disease. You find a node, it's EBV positive, you know it came from the nasopharynx. Hard as you look, you cannot find it in the nasopharynx. That is nasopharyngeal carcinoma with T0 disease. Let's talk about some of the differences between AJCC7 disease and the new AJCC8 disease. Previously, pteragoid and pre-vertebral muscle involvement would render you as T4 disease, but now we're dropping that down. It's only T2. We've used some more precise terminology for T2 and T4. We are more clear. For example, caudal border of the cricoid cartilage replaces the supercovicular fossa, which is too vague. And we've taken N3A and N3B, we don't talk about that anymore, it's N3. Here's a picture depicting the differences between the old AJCC7 and the new AJCC8. Notice that T2 disease now includes the medial lateral pteragoid muscles, those used to be four. That T2 disease now includes that pre-vertebral musculature and the carotid space there. So all of that is now just T2 disease. If you want to get T4 disease, you have to get all the way out in the masticator space or parotid gland.