What is the differential for this lesion?
The differential includes pituitary macroadenoma (cystic / necrotic), craniopharyngioma, Rathke's cleft cyst, epidermoid / teratoma spectrum (without visible fat) and arachnoid cyst (although one would have to postulate haemorrhage as the density is higher than CSF).
What differential not mentioned above should be kept in the back of your mind due to the severity of clinical sequelae should it be missed?
Giant intrasellar thrombosed aneurysm. Although appearances are atypical, sticking a surgical instrument into it would be less than ideal, and as such it is worth always considering even if only to discount it.
Large predominantly low density pituitary fossa mass is noted which extends into the suprasellar cistern. The lesion is predominately low density, however, does demonstrate a peripheral high attenuation rim with some heterogenous signal intensity is seen particularly in the anteroinferior margin with possibly a small nodule adjacent to this. No calcification is identified. The pituitary gland itself cannot be identified. The sella is grossly expanded, however, no definite bony destruction is identified.