Amyloidoma of the skull base

Abstract

We report a case of a primary amyloidoma of the skull base. Plain radiography and CT showed a lytic, highly destructive lesion with multiple scattered calcifications within. MR imaging revealed that the tumor was isoto hypointense to muscle on T1-weighted images and extremely hypointense on T2-weighted images. In contrast to two previous reports, marked enhancement after the administration of contrast material was absent. Bone amyloidomas are very rare and are frequently misinterpreted as chondrosarcomas.

fig 1.

Images from the case of a 54-year-old man with primary skull base amyloidoma. A, High-resolution coronal temporal bone CT scan shows a permeated aspect of the normal bone of the basiocciput, with scattered foci of calcifications or remnants of destructed bone within. The lesion (asterisk) is centered on the right petro-occipital fissure (curved black arrow) and crosses the midline. The petro-occipital fissure on the opposite side (straight black arrow) is intact. B, High-resolution axial temporal bone CT scan. A soft-tissue component (white arrows) extends through the posterior wall of the sphenoid sinus. C, Sagittal spin-echo T1-weighted (840/12/3 [TR/TE/excitations]) MR image displays the lesion (arrows) as iso- to hypointense to muscle. D, Coronal spin-echo T1-weighted (840/12/3) MR image. E, Sagittal turbo spin-echo T2-weighted (4416/128/1) MR image shows the lesion affecting the clivus (arrows) with very low signal intensity, similar to that of the air in the sphenoid sinus (S). F, Coronal contrast-enhanced spin-echo T1-weighted (840/12/3) MR image shows poor localized contrast enhancement (arrows).

fig 2.

Microscopic image. Congo red staining of the mass found in the sphenoidal sinus shows a marked thickening of the mucosa due to deposits of amyloid presenting as dark amorphous structures (arrows). The ciliary epithelium is well shown (curved arrows)