We report a case of PEComa (or perivascular epithelioid cell tumor) in an unusual articular localization in a 13-year-old boy. The tumor, of 4 cm in diameter, showed an infiltrative pattern and was composed of both epithelioid and spindle cells with clear to granular eosinophilic cytoplasm and some multinucleated giant cells. Focal nuclear pleomorphism was present and we found up to 2 mitotic figures /50 high power field. There was no necrosis. Immunohistochemistry showed HMB-45 and smooth muscle actin positivity. Ultrastructurally, premelanosomes were present. Some rare cases of PEComa were reported in the soft tissues. The immunohistological profile (HMB-45 and smooth muscle actin positivity and PS-100 negativity) is helpful to the diagnosis. The histological prognostic criteria of these tumors are not well established. We discuss here the differential diagnosis, notably clear cell sarcoma of soft tissue.