Hepatic perivascular epithelioid cell tumor: A rare mesenchymal tumor with epithelioid features: A case report.

Perivascular epithelioid cell tumors (PEComas) are rare mesenchymal neoplasms characterized by distinctive histological and immunohistochemical features. The tumor family originally included renal angiomyolipoma and pulmonary clear cell 'sugar' tumor. The present report describes a case of a hepatic PEComa in a 43-year-old man with no comorbidities and otherwise good health, who presented with abdominal discomfort and right upper quadrant tenderness. Laboratory findings were unremarkable. The patient underwent robotic-assisted left hemihepatectomy, and the results indicated negative margins. Histologically, the tumor consisted of epithelioid, polyhedral cells with central to eccentric nuclei and abundant eosinophilic cytoplasm, arranged in nests and separated by a delicate capillary network. Central necrosis was present, closely resembling hepatocellular carcinoma. Immunohistochemistry demonstrated strong expression of Melan-A and HMB-45, focal positivity for smooth muscle actin, and negativity for other lineage markers. The Ki-67 proliferation index was <5%. CD34 immunostaining demonstrated strong positivity in the endothelial cells, thereby highlighting the rich capillary network associated with the tumor. Molecular analysis supported the diagnosis. Next-generation sequencing identified pathogenic variants in TSC2 (exons 10 and 27), while fluorescence in situ hybridization excluded a TFE3 gene rearrangement at Xp11.23, ruling out TFE3-associated PEComa. The current case illustrated the diagnostic challenges of hepatic PEComas, given their rarity and morphologic overlap with primary liver tumors. It emphasizes the necessity of integrating histopathology, immunohistochemistry and molecular testing for accurate diagnosis, thereby guiding appropriate clinical management and avoiding misclassification.