[Polypoid PEComa: case report and literature review]

PEComa group is a heterogeneous group of rare mesenchymal tumors supposed to derive from perivascular cells and characterized by a coexpression of myogenic and melanocytic markers. We describe an 11-year-old female patient presenting a 2 cm ulcerated rectal polyp, exteriorized by anus, which was totally resected. Morphologically, this tumour was composed of cells arranged in nests or large cords separated by fibrous stroma, with abundant clear cytoplasms and with round regular small nuclei without atypia. There was no necrotic area and mitotic activity was very low. Immunohistochemically, the tumours cells stained for HMB45. Only 17 cases have been reported in literature and this case is the 18th. Here, we present a literature review focusing on both malignancy criteria and differential diagnosis.