Clear cell sarcoma arising in the pelvic peritoneum

초록

Clear cell sarcoma (CCS), also previously referred to as “malignant melanoma of soft parts,” is a very rare and aggressive soft tissue neoplasm, comprising approximately 1% of all diagnosed sarcomas. It occurs most commonly in the extremities, near aponeuroses and tendons of young adults. CCS is more common in female than in male patients and is linked to a high tendency of developing regional or distant metastases. Occurrence of this tumor on sites other than the extremities is extremely rare. We recently report the female case of CCS arising in the retroperitoneum and occupying the pelvic cavity. A 27-year-old woman, without any remarkable medical history, presented to our hospital with a palpable abdominal mass in the right lower quadrant of 6 months. She related that the mass had remained stable for 4 months, with no pain or increase in size. Two months prior to presenting at the hospital, she reported that the mass had started to enlarge, elicit pain. Physical examination revealed a tender firm mass with an irregular surface in the right lower quadrant of abdomen measuring approximately 4.0 x 3.0 cm. Magnet resonance image revealed a heterogenous peripheral enhancing mass adjacent to the right external iliac vessels that was solid with necrotic areas. This mass was protruded toward the anterior abdominal wall muscle, which was judged to be a direct tumor invasion. At the time of admission, her serum CA-125, CA19?9, carcinoembryonic antigen (CEA), and other tumor markers for germ-cell tumor; i.e., α-fetoprotein and human chorionic gonadotropin β subunit, were all within normal ranges. Laparotomy revealed a lump of cystic mass measuring 4.0 x 3.0 x 2.5 cm and containing chocolate-colored materials that was partly solid and cystic changed. Frozen section was diagnosed as "primary malignant melanoma". This tumor was resected as completely as possible during surgery. The immunohistochemical analysis showed positive staining for HMB45, S100 and SOX10.