Ewing's sarcoma / primitive neuroectodermal tumor of the kidney.

A 42-year-old female presented with right back pain. The CT scan revealed a 72-mm space-occupying lesion in the middle portion of the right kidney. No metastasis was proven. She underwent laparoscopic radical nephrectomy and lymph node disection. The histopathological examination revealed a high-grade primitive small round tumor the cells of which were strongly positive for CD99 and vimentin. Fluorescence in situ hybridization analysis using a DNA probe for the Ewing sarcoma breakpoint region 1 (EWSR 1) on chromosome 22g12 revealed a rearrangement of the EWSR 1 locus. The diagnosis was Ewing's sarcoma / primitive neuroectodermal tumor of the kidney. She underwent 13 cycles of chemotherapy, and has no evidence of recurrence 19 months after surgery.