The patient went on to have surgery.

Histology

The sections show moderately cellular pituitary adenoma comprising sheets and nests, surrounded by vascularized stroma.  The tumor cells have mildly enlarged round nuclei, finely granular chromatin and moderate amounts of eosinophilic cytoplasm. Elsewhere, there is evidence of apoplexy with tumor necrosis and hemorrhage. Granulation tissue with scattered chronic inflammatory cells is present. There is a small amount of normal anterior pituitary gland tissue present.

Scattered tumor cells are weakly positive for growth hormone. Entrapped prolactin positive cells are noted. Immunostains for the other pituitary hormones are negative. The Ki-67 index is difficult to determine as there are scattered positively stained inflammatory cells.

FINAL DIAGNOSIS: Somatotroph adenoma with evidence of apoplexy.