Close
MICROSCOPIC DESCRIPTION:
Paraffin sections show fragments of a moderately hypercellular tumour. This is composed of plump spindle cells arranged in loose fasciculi in a fibrous and vascular stroma. A palisaded arrangement of nuclei is noted in some areas. No mitotic figures or areas of necrosis are seen. No normal anterior pituitary tissue is included.
Immunohistochemistry shows strong nuclear staining for TTF-1 in tumour cells and strong cytoplasmic staining for S-100 protein. No staining for GFAP, synaptophysin, SOX10 or epithelial membrane antigen (EMA) is seen in tumour cells. The topoisomerase labeling index is <1%. The features are of spindle cell oncocytoma.
DIAGNOSIS: Spindle cell oncocytoma.