Large renal angiomyolipoma

Case contributed by Mohammadtaghi Niknejad


Right flank pain and fullness on physical exam.

Patient Data

Age: 35 years
Gender: Female

A large fat containing mass is seen in the right perinephric space, which displaces the right kidney, right adrenal gland, right lobe of the liver and IVC anteriorly. The mass originated from the upper pole of the right kidney, and large vascular structures are also observed within the mass. There are no signs of local invasion and no regional enlarged lymph nodes. 

A 12 mm mass is seen at the 5th hepatic segment that is hypersignal on T2WI and hyposignal on T1WI. After contrast media injection shows peripheral nodular enhancement with centripetal extension compatible with small hemangioma.

Case Discussion

The patient underwent a right radical nephrectomy.

Histopathology report:

Macroscopy: RIF, labeled as right radical nephrectomy specimen, consists of a kidney measuring 10x6x3 cm, with multiple yellow colored masses (intra-renal masses, D=2 cm to 2.8 cm) and two masses in perirenal fat, measuring 20x7x6 cm and 16x12x5 cm. A ureter measuring 6 cm long is seen. No enlarged lymph node is detected. Adrenal tissue, measuring 4.5 cm. SOS: 14/5.

Microscopy: Sections showing renal tissue, composed of mature adipose tissue, branching vascular tissue and stromal components with spindle cells and oval shaped nuclei. Eosinophilic cytoplasm (epithelioid appearance) and nuclear pleomorphism are seen. No mitoses. 
Adrenal is free. 

Diagnosis: Right renal angiomyolipoma

Notice that retroperitoneal liposarcoma invading the kidney could be considered in the differential list, but a large vessel extending into the renal cortex is suggestive of angiomyolipoma; liposarcoma is hypovascular. Also, renal parenchymal defect at the site of tumor contact favors exophytic angiomyolipoma - claw sign.

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