Clear cell sarcoma of soft tissues is a very rare, malignant soft tissue tumor that usually arises in the extremities, with a predilection for the lower limbs. This report presents a 45-year-old male with a painless mass in the right lumbar region for one year. Magnetic resonance imaging showed a 3.6×3.2×1.5-cm soft tissue mass of the right lumbar region. The tumoral cells had pleomorphic nuclei and large amounts of clear cytoplasm, and a proportion of the cells contained melanin. Immunohistochemical analysis was performed, which identified that the cells were positive for S-100, MITF and HMB-45 tumor markers. The patient underwent a postoperative chemotherapy protocol and had no local recurrences at one year post-surgery.
Keywords: MITF; S-100; clear cell sarcoma of soft tissues; melanin.