Collision tumor of spindle cell lipoma arising from perirenal tissue and acquired cystic disease-associated renal cell carcinoma: A rare case report.

Introduction: Collision tumors are a rare phenomenon defined as two or more histologically distinct tumors that are in contact with each other.

Case Presentation: The patient was a man with a history of end-stage diabetic nephropathy under hemodialysis treatment for 15 years. A plain computed tomography scan showed a 4.