Immunohistochemistry indicated FLI-1(+), CD99(+), Vimentin(+), CyclinD1(+), WT-1(+), EMA(+), Bcl2(-), Ki-67(+) 60%, CD56(-), CK(-), CD34(-), Desmin(-), and SMA(-), which suggested that renal clear cell sarcoma may not rule out renal cell carcinoma. This evidence concerns the gene CD99 and hereditary clear cell renal cell carcinoma.