Malignant angiomyolipoma in the liver: a case report with pathological and molecular analysis

Malignant angiomyolipoma (AML) of the liver is rare. We report a case of AML with malignant transformation and metastases. A 30-year-old man had developed giant hepatic masses. Microscopically, the periphery of the tumor showed components of classic hepatic AML, but the central region contained atypical epithelioid components with extremely pleomorphic and hyperchromatic nuclei with frequent mitotic figures. Immunohistochemical analysis revealed that the epithelioid cells were positive for HMB-45 and smooth muscle actin. Furthermore, the atypical epithelioid cells displayed P53 immunoreactivity and mutation at exon 7 for p53. The tumor showed a typical monoclonal pattern but no loss of heterozygosity or microsatellite instability. Markedly atypical epithelioid cells with vascular invasion, distant metastasis, and fatal outcome were interpreted as malignant characteristics of hepatic AML. It is suggested that large tumor size, pleomorphic nuclei with high proliferation activity, and P53 immunoreactivity may predict the existence of malignant transformation of hepatic AML.