Case #20

Frozen section diagnosis: Angiomyolipoma of the kidney.

Pathology and comment: The differential diagnosis of angiomiolipoma vs. renal cell carcinoma is one of the most difficult especially in needle biopsy. For the diagnosis of angiomyolipoma the demonstration of vessels with thick wall, large lipid drops in the cells and pale spindle cells (smooth muscle) is very helpful. Unfortunately these structures are not always well demonstrable in needle biopsies. In these cases (clinically suspicion of angiomyolipoma) we recommend the removal of the whole lesion and then definitive diagnosis will be made on the tumor resection specimen.