MICROSCOPIC DESCRIPTION: Sections show a hypercellular tumour composed of solid sheets nests and trabeculae. Tumour cells contain scant granular eosinophilic cytoplasm, round nuclei with finely granular chromatin and inconspicuous nucleoli. No mitoses are seen. No normal anterior pituitary tissue is included. There is extensive tumour coagulative necrosis, consistent with recent haemorrhagic infarction. Immunohistochemical results for pituitary hormones show focal FSH positive staining. The GH, LH, TSH, ACTH and Prolactin immunostains are all negative. The Topoisomerase proliferation index is approximately 1%.
DIAGNOSIS: Pituitary tumour: Silent gonadotroph cell pituitary adenoma with features of recent haemorrhagic infarction (pituitary apoplexy).