Cytologic analysis of renal angiomyolipoma: a comparison of radiologically classic and challenging cases.

Abstract

Angiomyolipoma is a benign kidney tumor with distinctive pathologic and clinical features. Because the prognosis differs from many other renal and retroperitoneal tumors, accurate diagnosis on cytologic material may be important for appropriate management. A retrospective analysis of cytologic material from eight patients with histologically confirmed angiomyolipomas was performed. The findings are described. Three cases were diagnosed radiologically as angiomyolipoma, three were diagnosed as renal cell carcinoma, one was diagnosed as a "renal mass," and one was diagnosed as a fat-containing adrenal tumor. Compared with the tumors that were suggestive radiologically of angiomyolipoma, tumors that were suspicious radiologically for renal cell carcinoma tended to contain less fat on cytologic examination. One fat-containing tumor was not diagnosed as angiomyolipoma because the tumor was believed to be adrenal in origin. Cytologically, cohesive stromal fragments were comprised of cells ranging from epithelioid to elongate. Stromal atypia was present in 7 of 8 cases (88%) but was marked in only 2 cases (25%). Thick-walled vessels were noted in 3 of 8 cases (38%). The cytologic diagnosis of angiomyolipoma is difficult in cases in which the radiologic diagnosis is not clear. The liberal use of immunostains is advised in the evaluation of stromal renal tumors.