 This first case is a 60-year-old man with a mass in the face, particularly in the nasal cavity area. Here's an axial T2-weighted image on the viewer's left, a coronal MRI, T1 contrast-enhanced image. There is a large mass filling the left maxillary atrium, spilling over the infundibulum into the hiatus, semilunaris, and truncating the angsinate process, which isn't seen. It extends all the way up into the ethmoid area, and it has a somewhat unusual convoluted appearance on the axial projection. You know, the differential diagnosis of tumors that occur in the maxillary atrium are pretty limited. You know, the most important one would be squamous cell carcinoma. And that's going to be very difficult to differentiate from its look-alike, the inverting papilloma, and of course they are related. About what percent of inverting papillomas actually have squamous cell carcinoma? Yeah, you'll read that the number with squamous cell carcinoma is about 11%. Our experience is it's a lot more frequent than that. I would say 50, 60 even. So it's a very serious problem and an important point to bring up if you're making that diagnosis of that connection between the two. I think what tends to happen is these are very difficult, inverting papillomas, which this by the way is, are very difficult to diagnose on nasoendoscopy. So you fish around for a while, you might find it, you take it out, then it comes back, then it comes back again. So the recurrence rates are extremely high. And eventually, probably one of the reasons why that number of 11% is low is these degenerate into squamous cell carcinoma. Now some of the checklist high points are whether it invades the foramenal valley, which we don't have time to show in this particular vignette example. You also want to look at the floor of the orbit, which is not invaded in this case. You want to look at the floor of the anterior phos of the cranium, which is intimately involved in this case. Inverting papillomas tend to be epicenter right over the unxinate process because they start in the nasal cavity along the lateral mucosa. Not in the maxillary antrim, where 85% of all squamous cell carcinomas are found. So a few tip-offs that you're dealing with, a large inverting papilloma as opposed to a squamous cell carcinoma. First on the axial T2, it's a very convoluted looking lesion. Some people describe this as a cerebraform appearance. Second, a squamous cell carcinoma, unlike an inverting papilloma, tends to grow into and through the lateral maxillary sinus wall and through the inferior orbital wall. It may go into the cranial fossa. It grows through the foramenal valley, which this one didn't. And about 15 to 20% present with lymph nodes in the jugular digastric chain or the retroferringial space, which this patient didn't have. So those are some of the checklist tip-offs to differentiate squamous cell carcinoma from the cerebraform inverting papilloma, which is epicenter right here and is a diagnosis in this case. Sound good? It does. And just to kind of boil it down, you know, we're in surgery, so we're not big on things like knowledge, so I try to limit those things. So there's two things I remember about this diagnosis. Dr. Palmer has mentioned them both. Location, un-synched process is going to be in the middle beatus, focused there, and also cerebraform. So I always think of this one as it's the brain that got shoved up somebody's nose. Okay? So you want to limit your, don't patch yourselves, okay? Be like us in surgery. And this is an excellent diagnosis to make, as I say, not always that easy. And it does look very cerebraform here. It looks like some gyri and sulci here, which is a real tip-off to the diagnosis, inverting papilloma.