Malignant hepatic angiomyolipoma: report of a case and review of literature.

Hepatic angiomyolipoma, a constituent of the group of tumors showing differentiation resembling perivascular epithelioid cells, is primarily appreciated in its benign form. Regardless of their location, this family of tumors is characterized by the presence of mature adipocytes, blood vessels, and spindle-epithelioid cells. These tumors also possess similar immunohistochemical profiles, including positivity for melanocytic (HMB-45) and smooth muscle (smooth muscle actin) markers. Here, we present a case of malignant hepatic perivascular epithelioid cells that was initially confined to the liver, treated by resection, and subsequently recurred within and metastasized beyond the liver. We take this opportunity to report the fourth case of malignant hepatic angiomyolipoma (HAML) and review the literature. We will discuss the features that aid in distinguishing between benign and malignant HAML, and their similarities. In summary, the common features of both benign and malignant HAML include the following: the 3 basic histologic components of AML, expression of melanocytic and smooth muscle markers, invasion into adjacent normal parenchyma, and cytologic atypia. The unique features of malignant HAML are as follows: clinical evidence of aggressive behavior such as metastasis or death owing to disease, coagulative necrosis, and loss of CD 117 expression.