MRI demonstrating features consistent with a pituitary macroadenoma.

The patient went on to have a resection. 

Histology

Sections revealed sheets of tumor cells with a rather uniform round to oval nuclei without mitosis or atypia separated by the thin sinusoidal vascular network within foci of hemorrhage. No necrosis. Ki67 proliferative index is low(about 1%).

Final diagnosis: pituitary macroadenoma.