The tumor cells are ovoid, epithelioid, or spindled and have uniform nuclei with fine chromatin and inconspicuous nucleoli. Mitotic figures may be seen but are not abundant. The staging of clear cell sarcoma of kidney is done by the National Wilms Tumor Study staging scheme. Treatment consists of surgery followed by chemotherapy and radiation. The addition of doxorubicin to a regimen consisting of vincristine and actinomycin has reduced the overall mortality. Delayed relapses may occur as many as 10 years after the original diagnosis, The most frequent site of relapse is bones.