Perinephric myxoid pseudotumor of fat in kidney transplant recipients: A single-center experience and review of the literature

Perinephric myxoid pseudotumor of fat (PMPF) is a very rare, benign perirenal mass that has been described in patients with advanced and inflammatory kidney disease. On imaging, PMPF can mimic benign and malignant lesions ranging from simple cysts to poorly differentiated malignant liposarcoma. Histologically, it consists of adipose cells, myxoid stroma, spindle cells and inflammatory cells, mainly lymphocytes. Herein, we report on our center's experience with PMPF in kidney transplant recipients with allograft loss presenting for re-transplant evaluation and provide a review of the existing literature. PMPF often presents as an incidental radiologic finding in end-stage kidney disease patients undergoing evaluation for re-transplantation. It may represent a localized reaction to renal parenchymal inflammation often caused by recurrent rejection, or chronic immunologic intolerance of previous allografts. PMPF is benign but should be differentiated from malignant entities such as well-differentiated liposarcoma.