Primary perivascular epithelioid cell tumor (PEComa) of the liver: report of a case.

PEComa is very rare mesenchymal neoplasm which is formed by perivascular epithelioid cells and is characterized by dual melanocytic and myoid differentiation. Up to now only a very few cases of PEComa of the liver have been described worldwide. We herein present a patient who underwent a right hemihepatectomy for a huge tumor which could not be identified by imaging investigations. A final histopathologic examination revealed a benign epithelioid tumor with a solid growth pattern, abundant vascularity, and frequently dilated vascular channels. Immunohistochemically, the tumor cells were strongly positive for HMB-45, moderately positive for actin, and faintly positive for S-100, respectively. Based on the above findings, a diagnosis of a primary clear cell "sugar" tumor was established. Because the natural history of PEComas is mostly unpredictable, the patient has been closely followed up; however, no recurrence has so far been observed. Immunohistochemical findings play a crucial role in avoiding a misdiagnosis, and a surgical resection with an adequate margin of healthy tissue remains the gold standard of treatment. A long-term periodic follow-up is reasonable in all cases presenting with PEComa.