What is the main differential diagnosis?
Pituitary macroadenoma, papillary craniopharyngioma, lymphocytic hypophysitis, metastasis.
What features are unusual for a macroadenoma?
Probable dural thickening anteriorly, small pituitary fossa (no remodelling), dumbbell shape to the tumour and irregular margins.
MRI of the pituitary demonstrates a soft tissue mass filling the fossa, extending up along the infundibulum and into the left cavernous sinus.