The patient went on to have a resection. 

Histology

MICROSCOPIC DESCRIPTION:

The sections show a moderately hypercellular tumor. This is composed of lobules of cells with uniform round and oval vesicular nuclei and a variable amount of pale eosinophilic cytoplasm. Separate from the lobules, there is a haphazard arrangement of variably sized solid aggregates of tumor cells within a fibrous stroma. A narrow rim of normal anterior pituitary tissue is present along one edge of the tumor. No mitotic figures or areas of necrosis are identified.

Immunohistochemistry shows patchy strong staining in tumor cells for LH and there is strong diffuse nuclear staining for steroidogenic factor (SF-1). Tumor cells also show moderate staining for synaptophysin. Several small cystic structures, lined by Rathke's cleft type epithelium, are noted within the tumor. Epithelial cells lining these structures show strong cytoplasmic immunostaining for pancytokeratin AE1/AE3. Scattered S-100 +ve folliculo-stellate cells are noted admixed with tumor cells. No immunostaining for growth hormone, prolactin, ACTH, FSH, TSH, p40, GFAP, TTF-1, HBME-1 or cytokeratins CK7, CK20, CK5&6 and CK19 is seen in tumor cells. The topoisomerase labeling index is approximately 2%.

FINAL DIAGNOSIS:

Silent gonadotroph cell pituitary macroadenoma.