Multicystic renal oncocytoma.

The usual gross appearance of a renal oncocytoma is that of a well-circumscribed homogeneous tan-brown tumor with no evidence of necrosis or hemorrhage, but with a central fibrous scar. We describe a case of renal oncocytoma with the unusual gross appearance of a cystic tumor. While cystic change has occasionally been mentioned in an oncocytoma to our knowledge, this degree of cyst formation has not previously been described.