We reported a case of clear cell sarcoma. A 67-year-old man presented with a subcutaneous tumor on the left poples which had been first noticed 4 years before. He decided to visit our hospital, because recently the tumor suddenly increased in size. Physical examination revealed a large and firm subcutaneous tumor about 6 cm in diameter in the left poples. The tumor was excised with wide dissection of the overlying skin and with left inguinal lymphnodes. Histologically, the tumor wascomposed of round or polygonal cells with clear cytoplasm and vesicular nuclei. Immunohistochemically, the tumor was positive for S-100, HMB-45, NSE, vimentin and Leu-7, but negative for EMA and polykeratin. RT-PCR analysis did not show the expression of hybrid EWS/AFT-1 transcript. In electron microscopy, some melanosomes were found in the tumor cells. Although it is difficult to distinguish between clear cell sarcoma and malignant melanoma with the unknown primary site, we diagnosed this tumor as clear cell sarcoma in clinical and histological respects. [Skin Cancer (Japan) 2001; 16: 349-352]
