OBJECTIVE To describe the pathologic features in four cases of hepatic angiomyolipoma, a rare benign mesenchymal tumor of the liver. METHODS Retrospective analysis of surgical specimens from four patients, with immunohistochemical and flow cytometric studies. RESULTS None of the patients carried a diagnosis of tuberous sclerosis. All four tumors were large and well circumscribed, and one patient had multiple lesions. The neoplasms were composed of numerous vessels and exhibited a predominance of epithelioid smooth muscle cells. The low amount of fat in these four cases was not sufficient to produce characteristic images that would allow diagnosis of angiomyolipoma before surgical resection. All tumors exhibited strong staining with HMB45 and anti-smooth muscle actin antibodies, whereas no positivity was observed with estrogen and progesterone receptor antibodies. Flow cytometry revealed a diploid DNA pattern in all cases. CONCLUSIONS Our four cases demonstrate that it is difficult to differentiate hepatic angiomyolipoma from other liver tumors when the amount of fat is low. HMB45 positivity of smooth muscle cells appears to be very helpful in reaching a pathological diagnosis of hepatic angiomyolipoma. The DNA-diploid pattern observed in all cases could be considered a new argument for the benign nature of hepatic angiomyolipoma.