Hepatic perivascular epithelioid cell tumors-not otherwise specified: a case report.

OBJECTIVE: Neoplasms of perivascular epithelioid cells (PEComas) are characterized by epithelioid to spindle cells with eosinophilic to clear cytoplasm, an intimate relationship with blood vessels, and coexpression of myoid and melanocytic immunohistochemical markers. While most reported hepatic PEComas, such as angiomyolipoma (AML), behave in a benign fashion, emerging PEComas cases without typical characteristics require further clarification. We report a case of primary hepatic perivascular epithelioid cell tumors-not otherwise specified (HPEComas-NOS) with untypical pathological and immunohistochemical features compared to those of the benign hepatic AML cases. HPEComas-NOS may represent a special type of PEComas classified as having "malignant potential" or at "high risk of aggressive behavior", suggesting the need for further clarification of hepatic PEComas and long-term follow-up of patients with HPEComas-NOS.