Desmoplastic small round cell tumor of the kidney in childhood.

BACKGROUND: Desmoplastic small round cell tumor (DSRCT) is a rare malignant tumor that generally manifests as abdominal paraserosal masses and affects mainly male adolescents and young adults. When presenting within visceral organs, the diagnosis of DSRCT poses significant difficulties.
METHODOLOGY: Four primary renal DSRCT in children diagnosed during a 3-year period are the basis of this report. The medical records and pathologic material were reviewed, including immunohistochemical, ultrastructural, and cytogenetic/molecular studies.
RESULTS: The age at presentation was 6 to 8 years, and all children presented with a left renal mass. The tumors measured 3.7 to 13.4 cm and consisted of nests, cords, or sheets of small undifferentiated cells with foci of necrosis and calcification. Desmoplasia was not seen. Tumor cells were immunopositive for vimentin, WT-1 (monoclonal and polyclonal), desmin, cytokeratin, and epithelial membrane antigen. A distinct paranuclear dotlike pattern was observed with vimentin and desmin. Tumor cells possessed rare or focal immunoreactivity for platelet derived growth factor-A and transforming growth factor-beta3, which have been implicated in the pathogenesis of desmoplasia in DSRCT. The EWS-WT1 t(11;22)(p13;q12) translocation was demonstrated in all 4 tumors by fluorescence in situ hybridization and/or reverse transcription-polymerase chain reaction.
CONCLUSIONS: DSRCT should be considered in the differential diagnosis of renal tumors composed of small round cells. Undifferentiated morphology and lack of desmoplasia contribute to the difficulty in its recognition. Ancillary studies such as immunohistochemistry may suggest the diagnosis, but cytogenetic and molecular genetic studies are required for confirmation.