The pituitary gland is enlarged by a non-enhancing well circumscribed lesion which extends above the diaphragma sella and impinges upon the optic chiasm.
Note: On fat sat T1 C+ images it is difficult to distinguish intrinsic T1 from enhancement. Looking at the non fat sat T1 C+ coronals confirms lack of enhancement.
Features therefore suggest the diagnosis of a Rathke's cleft cyst or adamantinomatous craniopharyngioma although the absence of calcification and age make this less likely. A necrotic adenoma is another possibility.