Hepatic Perivascular Epithelioid Cell Tumor (PEComa): A Case Report.

Perivascular epithelioid cell tumors (PEComas) are a rare group of mesenchymal neoplasms composed of perivascular epithelioid cells. While commonly found in the kidney, uterus, and soft tissues, PEComas of the liver are exceedingly rare.  We present a case of a PEComa incidentally discovered in a 73-year-old female patient undergoing evaluation for abdominal pain. Imaging revealed an indeterminant mass in the left hepatic lobe without internal color uptake on Doppler flow. Histopathological evaluation was consistent with PEComa. The tumor was mainly composed of well-circumscribed epithelioid and spindle cell lesions with smooth muscle differentiation. Immunohistochemical staining was positive for smooth muscle actin (SMA), human melanoma black 45 (HMB 45), and Melan A.  PEComas are usually detected incidentally during workup for other reasons. Diagnosis is based on histopathological evaluation, and although most of the cases reported in the literature were evaluated after surgical resection, some of them were diagnosed after the image-guided biopsies, as we did in our case. This entity of tumors needs further studies on their natural behavior, as some malignant cases were reported. In addition, a clearer approach to diagnosis and treatment needs to be established, and more prognostication tools and radiographic characterization are needed.