[Differences in morphology and immunohistochemistry between hepatic angiomyolipoma and renal angiomyolipoma]

To investigate the clinicopathological and immunohistochemical characteristics of hepatic angiomyolipoma (AML) and renal AML, and to compare the similarities and differences between the two.

Hematoxylin-eosin staining and SP immunohistochemical staining were performed on the specimens resected during operation of 12 cases of hepatic AML, 2 males and 10 females, aged 41, and 38 renal AML cases, 14 males and 24 females, aged 43. Wilcoxon rank test was made on the proportions of the 3 kinds of myoid cells and fat tissues.

All tumors were composed of three basic components: blood vessels, fatty tissue, and myoid cells epithelioid, spindle, or intermediate in shape. Epithelioid cells accounted for more than 50% of the cells in 6 out of the 12 hepatic AML cases often with apparent cellular and nuclear atypia (12/12), and accounted for less than 25% in all renal AML cases. Spindle-shaped cells were scarcely observed in hepatic AML and were common in renal AML. Nuclear atypia was observed in 20 out of the 38 renal AML cases, 18 cases being mild and 1 being moderate. Fat cells accounted for less than 50% in hepatic AML, and more than 50% in renal AML (P = 0.001). Extramedullary hematopoietic tissue was often seen in hepatic AML but never observed in renal AML. Strong positivity of HMB45 and focal positivity of SMA were common in hepatic AML and strong positivity of SMA and sporadic positivity of HMB45 were observed in the renal AML specimens.

The histological composition of AML is highly variable in the proportion and distribution of the 3 component cells between hepatic AML and renal AML.