Melanoma markers in angiomyolipoma of the liver and kidney: a comparative study.

Abstract

Melanoma markers, especially the new microphthalmia transcription factor (mitf), have not been previously compared in hepatic and renal angiomyolipomas. To evaluate expression of the novel melanocytic markers mitf and tyrosinase in angiomyolipomas, and to compare these markers with the established markers HMB-45 and melan-A in both hepatic and renal tumors. Clinical, histopathologic, and immunohistochemical features of 15 hepatic angiomyolipomas were compared with those of 10 renal angiomyolipomas. No significant differences between patients with hepatic angiomyolipomas and renal angiomyolipomas were found with respect to age, gender, race, and tumor size. Hepatic angiomyolipomas exhibited a predominance of the epithelioid smooth muscle cell component, in contrast to their renal counterparts, which were predominantly spindled. The smooth muscle cells expressed HMB-45 in 100% of cases in both groups, melan-A in 14 of 15 hepatic angiomyolipomas and 8 of 9 renal angiomyolipomas, mitf in 5 of 12 hepatic angiomyolipomas versus 6 of 10 renal angiomyolipomas, and tyrosinase in 3 of 12 and 2 of 10 hepatic angiomyolipomas and renal angiomyolipomas, respectively. The extent and intensity of immunostaining with HMB-45 and melan-A were dependent on whether spindled or epithelioid cells predominated; the epithelioid cells showed stronger and more widespread reactivity than the spindled cells. We believe that the best immunohistochemical marker for confirming the diagnosis of angiomyolipoma is HMB-45, followed by melan-A. Routine use of mitf and/or tyrosinase is not indicated.