Hepatic perivascular epithelioid cell tumors: Benign, malignant, and uncertain malignant potential

Abstract

In 2013, the World Health Organization defined perivascular epithelioid cell tumor (PEComa) as “a mesenchymal tumor which shows a local association with vessel walls and usually expresses melanocyte and smooth muscle markers.” This generic definition seems to better fit the PEComa family, which includes angiomyolipoma, clear cell sugar tumor of the lung, lymphangioleiomyomatosis, and a group of histologically and immunophenotypically similar tumors that include primary extrapulmonary sugar tumor and clear cell myomelanocytic tumor. Clear cell tumors with this immunophenotypic pattern have also had their malignant variants described. When localizing to the liver, preoperative radiological diagnosis has proven to be very difficult, and most patients have been diagnosed with hepatocellular carcinoma, focal nodular hyperplasia, hemangioma, or hepatic adenoma based on imaging findings. Examples of a malignant variant of the liver have been described. Finally, reports of malignant variants of these lesions have increased in recent years. Therefore, we support the use of the Folpe criteria, which in 2005 established the criteria for categorizing a PEComa as benign, malignant, or of uncertain malignant potential. Although they are not considered ideal, they currently seem to be the best approach and could be used for the categorization of liver tumors.

Keywords: PEComas; Liver; Pathology; Malignant; Benign; Uncertain malignant potential

Core Tip: Perivascular epithelioid cell tumors are rare mesenchymal tumors for which the diagnostic criterion appears to be exclusively histopathological. They are characterized by a proliferation of perivascular epithelioid cells and the coexpression of markers for smooth muscle and melanocytes. They mainly affect females and occur in almost all organs. The incidence of benign and malignant perivascular epithelioid cell tumor of the liver is much lower than in other organs. It is necessary to reinforce the notion that there are malignant variants located in the liver, which are more frequently described along with their histologic and immunohistochemical features.