This patient went on to have a partial nephrectomy.
MACROSCOPIC DESCRIPTION: "Partial nephrectomy": The specimen consists of a segment of kidney weighing 23g and measuring 42x52x30mm. Resection margins are inked. Serial sectioning reveals a well circumscribed, nodular, partly tan, yellow tumour 30x23x25mm. Tumour abuts the inked resection margins. Within the tumour there are focal areas of haemorrhage. There is no invasion beyond the renal capsule.
MICROSCOPIC DESCRIPTION: The sections of kidney show a circumscribed moderately hypercellular tumour enclosed within a fibrous capsule of varying thickness. Tumour cells have round oval and angulated hyperchromatic nuclei and a variable amount of cytoplasm which contains dense eosinophilc, PTAH positive granules. No mitotic figures or areas of necrosis are identified and no capsular or vascular invasion is seen. The adjacent renal parenchyma is unremarkable. Immunohistochemistry shows patchy staining for CK7 in tumour cells. Occasional CD10 positive cells are also noted.
FINAL DIAGNOSIS: Oncocytoma