Malignant angiomyolipoma of the liver: a hitherto unreported variant

Aims: After their original recognition in the kidney, angiomyolipomas (AMLs ) have been reported in the liver for more than 20 years. In the kidney, fi ve cases of malignant AML have been reported. We report the first case of m alignant hepatic AML. Methods and results: A 70-year-old female patient presented with abdominal discomfort. Clinical examination revealed a palpable liver. CT scan showed a polymorphous hypervascular lesion in the right liver lobe. A biopsy was t aken and resulted initially in a differential diagnosis between a hepatocel lular carcinoma, a metastatic tumour (possibly of renal origin) and angiomy olipoma (AML). After immunohistochemistry, a hepatic AML was suggested, giv en the immunoreactivity for HMB45/NKIC-3. The mass was resected 5 years lat er because of relapsing abscess formation. Gross examination of the resecti on specimen showed a focally encapsulated brown mass with focal necrosis. M icroscopic examination showed a tumour growing in sheets, separated by sinu soidal-like vessels. Most of the tumour cells had a large, polygonal, clear cytoplasm, often with eosinophilic condensation around the nucleus. There was prominent vascular invasion. Immunohistochemistry (reactivity for HMB-4 5, NKIC-3, S100 and alpha smooth muscle actin, negativity for cytokeratin a nd vimentin) and electron microscopy confirmed the diagnosis of monomorphic epithelioid AML with prominent vascular invasion. Seven months after tumou r resection, the patient died of recurrent disease. Conclusions: hlights the importance of immunohistochemistry and electron mi croscopy in diagnosing this type of tumour. Possibly, in the past, malignan t AML of the liver has been misdiagnosed as HCC.