Perivascular epithelioid cell tumor (PEComa) of the liver: a case report and review of the literature

Perivascular epithelioid cell tumor (PEComa) is rare entity and has been described only recently. By immunohistochemistry and genetics it belongs to the family of tumours which comprises angiomyolipoma, clear cell "sugar" tumor of lung, lymphangioleiomyomatosis and clear cell myomelanotic tumor of ligamentum falciforme/teres hepatis. We describe an unusual case of hepatic PEComa arising in a 55-year-old woman with previous history of glioblastoma. Histologically the tumor grew in expansive way, and was composed of clear and eosinophilic epithelioid cels, without vascular or lipomatous component characteristic of angiomyolipoma. There was mild nuclear pleomorphism, sporadic mitotic activity and haemorrhage without necrosis. On immunohistochemistry, the tumor was HMB-45+50, Melan-A and smooth muscle actin positive. Tyrosinase, S-100 protein, cytokeratin coctail, EMA, vimentin, muscle specific actin, CD10, TTF-1, hepatocyte, desmin and cyclin D1 were negative. Sporadic nuclear p53 positivity was seen. The main differential diagnosis of hepatic PEComa includes clear cell variant of liver cell adenoma and hepatocellular carcinoma, metastases of various clear cell carcinomas and metastasis of malignant melanoma. In respect of uncertain biologic potential of PEComa, long term follow up is indicated.