[A case of renal oncocytoma associated with acquired cystic disease of the kidney].

We report a case of renal oncocytoma associated with acquired cystic disease of kidney (ACDK). A right renal mass was incidentally found on an annual ultrasonography of the kidneys in a 56-year-old female patient who had been on maintenance hemodialysis for 6 years. Computerized tomography (CT) showed a right hypervascular renal mass, suggesting a renal cell carcinoma associated with ACDK. Right radical nephrectomy was performed. The post-operative pathological diagnosis was renal oncocytoma. Renal oncocytoma in ACDK is very rare, and the pathological characteristics of oncocytoma are discussed.