Renal angiomyolipoma

Case contributed by Assoc Prof Frank Gaillard


Right flank pain.

Patient Data

Age: Adult

Pre and post-contrast CT through the kidneys demonstrates a large fatty mass arising from the lateral aspect of the right kidney. There is a very prominent vessel centrally associated with central areas of soft tissue attenuation, some of which enhance, but other areas do not. These presumably represent areas of hemorrhage. 

This patient went on to have a right partial wedge nephrectomy.

MACROSCOPIC APPEARANCE: Specimen consists of a wedge of kidney measuring 5.5 X 4 X 2.5 cm that came with a soft fatty nodule bulging on its surface, measuring 13 X 9.5 X 8 cm, weighing in total 430 g. The external capsule is smooth and shows tan-purple hemorrhage. Cross-section of the nodule shows yellowish fatty tissues with focal hemorrhage that is surrounded by a well-defined capsule. The tumor partially replaces the renal parenchyma and extends into the peri-renal fat.

MICROSCOPY: It has typical features of angiomyolipoma with smooth muscle spindle cells, at times with an altered ovoid morphology, admixed and blending with thick-walled blood vessels and tumor adipose tissue. Occasional compact sheets of the smooth muscle mesenchymal component are present, with degenerative nuclear atypia. There is no significant mitotic activity and no evidence of malignant transformation.


  • angiomyolipoma of the kidney.
  • tumor size = 13cm.
  • acute hemorrhage within tumor.

Case Discussion

This case demonstrates typical appearances of a large angiomyolipoma. Best seen on the post-contrast images is a very large vessel which accounts for this tumor's predilection for spontaneous hemorrhage. 

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