DETECTION OF THE EWS WT1 GENE FUSION BY REVERSE TRANSCRIPTASE-POLYMERASE CHAIN-REACTION IN THE DIAGNOSIS OF INTRAABDOMINAL DESMOPLASTIC SMALL ROUND-CELL TUMOR/

We report two cases of intra-abdominal desmoplastic small round cell t umor with characteristic clinical, histological, immunohistochemical, and ultrastructural features. Fusion of the EWS gene on chromosome 27 and the WT1 gene on chromosome 11, resulting from the chromosomal tran slocation t(11:22)(p13;q12), was detected by reverse transcriptase pol ymerase chain reaction (RT-PCR) in both cases. This translocation has been previously reported in this type of tumor using either cytogeneti c or molecular biological techniques. Tumor tissue from both cases rev ealed no chimeric fusion transcripts characteristic of the Ewing sarco ma family of peripheral primitive neuroectodermal tumors or of alveola r rhabdomyosarcoma, two tumors in the differential diagnosis of intraa bdominal desmoplastic small round cell tumor. This report demonstrates the utility of molecular studies as an adjunct in the diagnosis of th is rare and aggressive tumor.