In the suprasellar cistern, in the midline, immediately posterior to the infundibulum is a lesion with a central fat density and peripheral calcification, its long axis pointing up towards the mammillary bodies which are either hypoplastic or compressed. The lesion centrally demonstrates fatty signal, which attenuates on fat-suppressed sequences. There is no solid or contrast-enhancing component. The calcifications, best seen on CT are located predominantly at the margins of the lesion. The optic chiasm is not compressed. The pituitary is normal in appearance. Ventricles are normal in size.
Features are characteristic of a suprasellar (hypothalamic) osteolipoma (a.k.a. ossified lipoma), a rare benign, usually incidentally identified mass of mesodermal origin. The differential includes a dermoid cyst which could have similar appearances, although calcification is uncommon, or far less likely a craniopharyngioma.