Huge renal lipoma with prominent hypervascular non-adipose elements.

A primary renal lipoma is a very rare neoplasm of the kidney and only 20 cases have been reported in the literature. We report a case of a huge retroperitoneal mass that presented as a hypervascular tumour with a prominent fat component, mimicking an angiomyolipoma or a liposarcoma in imaging studies. This finding presented a diagnostic challenge in terms of selecting medical versus surgical intervention. Surgical excision of the lesions was performed and the pathological evaluation revealed a renal lipoma with extrarenal growth.