|Micrograph of a renal oncocytoma.|
Signs and symptoms
Renal oncocytomas are often asymptomatic and are frequently discovered by chance on a CT or ultrasound of the abdomen. Possible signs and symptoms of a renal oncocytoma include blood in the urine, flank pain, and an abdominal mass.
Renal oncocytoma is thought to arise from the intercalated cells of collecting ducts of the kidney. It represent 5% to 15% of surgically resected renal neoplasms. Ultrastructurally, the eosinophilic cells have numerous mitochondria.
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In gross appearance, the tumors are tan or mahogany brown, well circumscribed and contain a central scar. They may achieve a large size (up to 12 cm in diameter).
The main differential diagnosis of renal oncocytoma is chromophobe renal cell carcinoma oncocytic variant, which like the renal oncocytoma has eosinophilic cytoplasm, but has perinuclear clearing and, typically, some degree of nuclear atypia.
- Cytokeratin AE1/AE3 +
- Vimentin -
- EMA +
- CK7 +/- parcellaire
- CK20 -
- CK19 -
- AMACR (Racemase) -
- S100 +
- c-kit (CD117) +
- Cadherin-E +
- TFE3 -
- CAM5.2 +
Renal oncocytoma is considered benign, cured by nephrectomy. There are some familial cases in which these tumors are multicentric rather than solitary. However, they may be resected to exclude a malignant tumor, e.g. renal cell carcinoma.
Micrograph of chromophobe RCC oncocytic variant, the main differential diagnosis of renal oncocytoma.
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