MICROSCOPIC DESCRIPTION: Paraffin sections show fragments of a moderately hypercellular adenoma. Tumour cells have mildly pleomorphic round and oval nuclei with vesicular chromatin and a variable amount of pale eosinophilic cytoplasm. These are arranged in solid sheets intersected by thin-walled capillaries. No mitotic figures or areas of necrosis are identified. No normal anterior pituitary tissue is included. Immunohistochemistry shows strong cytoplasmic staining for prolactin in tumour cells. No staining for GH, ACTH, LH, FSH, TSH, cytokeratin CAM5.2 or oestrogen receptor (ER) is seen in tumour cells. The features are of a lactotroph cell pituitary endocrine tumour. A small Rathke cleft cyst is noted in the CAM5.2 immunostained section. This is completely surrounded by the tumour.
DIAGNOSIS: Pituitary tumour: Lactotroph cell pituitary endocrine tumour; incidental small Rathke cleft cyst.
Slides courtesy of Prof. Michael Gonzales - RMH Pathology Department