Desmoplastic small round cell tumor of the kidney.

Desmoplastic small round cell tumor (DSRCT) is a rare, aggressive, malignant tumor usually present with widespread abdominal serosal involvement. Isolated cases occur in limbs, head and neck, and brain. We present a case of primary DSRCT of the kidney in a 41-year-old man. The tumor showed morphologic, immunohistochemical, and molecular characteristics similar to DSRCTs arising in other sites. Epithelial and mesenchymal markers were coexpressed in the tumor cells. RT-PCR analysis showed EWS-WT1 fusion transcripts resulting from the t(11;22)(p13;q12) reciprocal translocation. DSRCT should be considered in the differential diagnosis of small blue round cell tumors of the kidney.