 Let's take on a few more brain tumors and intraventricular cases. Let's begin with this infant with macro crania. We have an axial T2 spinneco MR, the presence of a mass with innumerable other findings, an axial T1 non-contrast, an axial flare non-contrast, a coronal T2 non-contrast, a coronal and axial T1 with contrast, a set of axial diffusion restricted images, an axial ADC map parametric image, and a sagittal T1 contrast enhanced image. Let's take our first question. The most likely diagnosis in this infant is a. Choreoplexus papilloma, b. Ventricular metastasis, c. Subapendemoma, d. Ventricular glioma, e. Ependemoma. You can pause if you wish. I'm going to move on to question number two. We're following as false regarding Choreoplexus papilloma. a. 50% in the atrium of the lateral ventricle, b. Left side more affected than right. c. Macro crania, nausea, vomiting. d. Calcifies 90% of the time. e. Hydrocephalus. Question number three. Which of the following is false regarding Choreoplexus papilloma? a. Hypercoic on ultrasound, b. 50% third ventricular roof, c. Robust contrast enhancement, d. When in the fourth, posterior medullary vellum and foramina of lusca, e. Extensive invasion equals Choreoplexus carcinoma. Let's turn back to our set of images and analyze them together. We begin with our axial T1 weighted image. A large mass, whose position is a little bit in question. Is it intraventricular or does it compress the ventricle? It is located in the region of the left lateral ventricle atrial trigone, which is a classic location in an infant for Choreoplexus papilloma. Yes, this is one of the unusual tumors in an infant, which is supratentorial. The coronal T2. Again, it's a little difficult to ascertain whether it's intraventricular, but there is no compressed left lateral ventricle. In other words, you can't see the ventricle compressed by an extra ventricular lesion, and that's because it's occupying the entire intraventricular space. There is a caven septum palusitum and verge, which is a variation. There is ventricular dilatation or hydrocephalus, either from obstruction or overproduction hydrocephalus. The temporal horns are enlarged. There's sub-fall scene shift. There is displacement of the uncus medially, worrisome for potential herniation of the brain, something that must be called out by you in your interpretation. The coronal contrast enhanced image demonstrates a large cauliflower-like mass, papillary, in configuration, in keeping with the name choride plexus papilloma. It's very frond-like. There is a little bit of inferior extension, so your differential diagnosis would continue to lie between choride plexus papilloma and carcinoma. The surrounding brain demonstrates extensive encephalomalacia, most consistent with a chronic infarction, perhaps related to compression of the key vascular feeders in this distribution. The diffusion-restricted image demonstrates diffusion restriction in the center of the lesion. I'm not sure that's particularly helpful in telling you what the histology of the lesion is, but the diffusion restriction is definite. For on the ADC map, there is low signal intensity, indicating decreased micromolecular movement or restriction of movement. Therefore, the velocity is low. The signal is low on the parametric image. The sagittal projection corroborates the intraventricular nature of the lesion. This is the one image that confirms that your lesion is like a belly button. It's an innie rather than an outie. It's inside the ventricle, for the ventricle lops over the top of it right there, as opposed to being compressed or displaced by it. Furthermore, look at that downward inferior extension into the temple horn. There's no question that this component of the lesion is intraventricular, corroborating the rest of the lesion as being intraventricular. Now let's go back to our questions. Let's begin with the first question. The answer is chloride plexus papilloma. Could it have been a carcinoma? Certainly. Sometimes only the histology will tell, but chloride plexus carcinoma was not a choice. It's an infant. It's a large papillary mass in the left lateral ventricle atrial trigone. You should reflexively choose chloride plexus papilloma. Ventricular metastases. In somebody under age two, really metastatic disease to the ventricular system, if you chose this, you're probably not very practical. Sub-apendimoma. Typically found in the inferior fourth ventricle, but it can be supra-tentorial, but it doesn't enhance very often. You don't find it in infants very often, so it's a very poor choice. Ventricular gliomas. Don't enhance intensely and under age two as a choice for an intraventricular lesion, also not very practical. The only other lesion that I think is a viable choice is appendimoma. But typically not under age two. Typically in the fourth ventricle, and when supra-tentorial, often in young adults or adults, involves surprisingly the brain parenchyma. So this one, too, is not a great choice. Question two. Which of the following is false regarding chloride plexus papilloma? The answer is D. It does not calcify 90% of the time. It calcifies around 20 to 25% of the time, but the rest of the answers are true. 50% involve the atrium of the lateral ventricle. It is true that the left side is more affected than the right. It is true that macro-crania, nausea, and vomiting are a common presenting complaint, and the reason is it's true that hydrocephalus is often associated with this tumor. Question number three. Which of the following is false regarding chloride plexus papilloma? And the answer is B. 50% do not involve the third ventricular roof, for that designation is often given to colloid cyst. No, this lesion has a marked propensity, as stated for the lateral ventricle, especially the atrial trigone, and especially the left side. But it is true. They are hyper-echoic on ultrasound. It is true that they have robust contrast enhancement like our very large papillary lesion in the ventricle. It is true that when they occur around the fourth ventricle, that they may involve the posterior medullary vellum and foramina of lusca. It is true that extensive invasion suggests the diagnosis of chloride plexus carcinoma. Let's talk a little bit about chloride plexus papilloma. First, chloride plexus tumors are not very common. There are only about 3% of pediatric brain tumors. They are only 0.5% of adult brain tumors, but they can be present at birth. They are World Health Organization Grade 1 lesions. Despite the fact that they can get very large, wreak havoc on the brain by virtue of hydrocephalus, which was present in this case. The hydrocephalus can be related to compression or overproduction hydrocephalus. As stated, lateral ventricle is most common. Especially in kids. And there is no gender predilection. Although there is a slight gender predilection for males if you break out the fourth ventricular ones alone. They can occur in multiple locations. In fact, 5% of the time they are in multiple locations. Chroid plexus papilloma and carcinoma are notorious for their ability to seed other loci in the brain. This is also true for the appendemoma, the medulloblastoma, and the glioblastoma multiforme of the adult. As you've seen, hydrocephalus is intimately associated with both the chroid plexus papilloma as well as the chroid plexus carcinoma. This is a tumor that occurs in the young, under age 5. And the overwhelming minority of these, fortunately, are chroid plexus carcinomas. The majority are benign. They're pretty soft. They are well circumscribed. They have been likened to the appearance of cauliflower. And I think ours looks quite a bit like cauliflower. Histologically, they are very similar in appearance when benign to regular chroid plexus anatomy. Hemorrhage and cyst formation may be seen. If we go back for a moment, here is a cyst associated with our tumor. There's another cyst associated with our tumor. Sometimes the cyst can be misconstrued with trapped ventricular tissue. They only calcify about 24% of the time, or as we said earlier, 20 to 25%. So that one choice, 90% calcify, is incorrect. They can extend from one ventricle to another, and our mass was extending from the lateral ventricle, the atrium, into the temporal horn. They can be attached by a vascular pedicle to the chroid plexus, and they can move, causing intermittent ventricular obstruction in much the same way that chroid or colloidal cyst, sorry, colloidal cyst will do the same thing, so-called colloid cyst of the entero superior third ventricle. On CT, they are iso to hyper-dense or iso-dense. There is intense enhancement. On a CTA or an MRA, you may see an enlarged colloidal artery. On MR, the T1 signal is iso to hypo-intense unless they have blood. The T2 signal is iso to hyper-intense, although may be low signal if they have intermittently bled, and there is citerotic accumulation. On MR, you may see vascular flow voids. On non-contrast MR, they are avid for iodine, they are avid for gadolinium, so on MR, the enhancement is also intense. Unfortunately, imaging alone cannot distinguish chroid plexus papilloma from chroid plexus carcinoma. In my experience, diffusion restriction is not helpful in differentiating chroid plexus papilloma from carcinoma. This concludes our discussion of chroid plexus papilloma, a tough lesion, relatively large, young patient, left lateral atrial trigone, calcifies 20 to 25% of the time, intense enhancement, looks like cauliflower, very papillary, closely associated with hydrocephalus, either overproduction or obstructive hydrocephalus. Let's move on to the next case, shall we?