Morphologic variants and immunohistochemical features of hepatic angiomyolipoma

Abstract

To study the clinicopathological characteristics, immunohistochemical features and differential diagnosis of hepatic angiomyolipoma (AML). The clinicopathological features of hepatic AML were systematically examined in 44 surgically resected tumor specimens, with additional immunohistochemistry study using 10 relevant antibodies. The tumors were composed of various amounts of three components, i.e. blood vessels, smooth muscle cells and adipose cells. According to the proportions of each of these tissue components, AML was subcategorized into the classical type (n = 13), myomatous type (n = 25), lipomatous type (n = 4), and angiomatous type (n = 2). Myoid cells displayed various morphology, including epithelioid, intermediate (ovoid or short spindle), spindle, oncocytic, and pleomorphic features. Hematopoietic elements were present as minor findings in eight tumors. Immunohistochemically, the tumor cells were strongly positive for HMB45 (44/44, 100%), SMA (38/38, 100%) and CD117 (30/38, 78.9%). A correct diagnosis of hepatic AML might be difficult due to its various growth patterns and cell types. HMB-45 positivity in the myoid cells is a key feature for hepatic AML. CD117 may be another useful ancillary marker for reaching a definite diagnosis.