ORIGIN AND BIOLOGY OF A TESTICULAR WILMS-TUMOR

A pure triphasic testicular Wilms' tumor, without teratomatous element s, was studied using multiple techniques. Carcinoma in situ (CIS), the characteristic precursor of testicular germ cell tumors of adults (TG CTs), was found in the adjacent parenchyma. Flow cytometric analysis s howed a single hypotriploid tumor stem line. Karyotyping of the tumor revealed some numerical and structural abnormalities, including an i(1 2p), the chromosomal marker of TGCTs. In situ hybridization supported the karyotypic findings, and showed a similar numerical distribution i n CIS and the tumor. Molecular analysis of the tumor illustrated that all short arms of chromosome 12, including i(12p), were of maternal or igin. No 12q deletions were detected. In spite of complete loss of the paternal 11p13 band, the zinc finger regions and exons 2 and 6 of the WT1 gene contained no aberrations. Therefore, this tumor suppressor g ene is not inactivated due to aberrations in the studied regions. In a ddition, all four WT1 alternative transcripts were expressed in the tu mor. No aberrations were found in chromosomal bands 11p15.5, 16q22.1, and 16q24. Both parental alleles of the human imprinted genes H19 and IGF2 were expressed in the tumor. This is the first report on the chro mosomal and molecular characterization of an extrarenal Wilms' tumor. Its germ cell origin was unequivocally demonstrated. Genes Chromosom C ancer 11:126-135 (1994). (C) 1994 Wiley-Liss, Inc.