Sinochoanal polyp and its variant, the angiomatous polyp: MRI findings

The angiomatous polyp corresponds to the vascular compromised nasochoanal p art of a sinochoanal polyp. We describe the MRI characteristics of such les ions in four patients. All patients had an angiomatous polyp, in three case s as part of an antrochoanal polyp, and in one case as part of a sphenochoa nal polyp. The unenhanced MR images depicted the typical appearance of a si nochoanal polyp, hypointense on T1-weighted and hyperintense on T2-weighted images. On gadolinium-enhanced MR images, the sinusal part showed little o r no peripheral enhancement; however, the nasochoanal part, corresponding t o the angiomatous polyp, showed strong enhancement. An angiomatous polyp mi mics a hypervascular mass lesion on enhanced MR studies. The anatomic locat ion and association with a sinusal polyp allows the correct diagnosis.