Renal sinus myelolipoma coexistent with renal pelvis papillary transitional cell carcinoma: a case report.

A unique case of renal sinus myelolipoma presenting as a mass coexistent with papillary transitional cell carcinoma is reported. The patient was a 64-year-old man with a history of bladder transitional cell carcinoma. He presented with gross hematuria and a filling defect in the renal pelvis on computed tomography scan. Pathological findings revealed an irregular myxoid fatty mass, in addition to high-grade papillary transitional cell carcinoma. The differential diagnosis included myxoid liposarcoma, myxoid variant of malignant fibrous histiocytoma (myxofibrosarcoma), and angiomyolipoma. Immunoperoxidase staining confirmed the presence of hematopoietic cells, whereas diagnostic histological and immunohistochemical features of liposarcoma, myxofibrosarcoma, and angiomyolipoma were absent. Myelolipoma and papillary transitional cell carcinoma appear to be unrelated coexistent entities in this case.