Heavily pigmented renal cell carcinoma: a case report, with review of the literature and differential diagnosis.

Clear cell carcinoma is the most common histotype among renal cell tumors. The prominent vascular network of sinusoidal vessels lined by delicate endothelial cells may often lead to hemorrhagic areas with secondary deposition of chunky birefringent hemosiderin granules. The finding of pigmentation other than iron, and in particular melanin deposits, in renal tumors is a rare occurrence that should lead to differential diagnosis with other primary and metastatic tumors of the kidney.