Unbalanced translocation of chromosome 3p in Wilms' tumor.

Genetic studies in Wilms' tumor have most commonly shown a deletion involving band 13 on the p arm of chromosome 11 in association with aniridia. Structural rearrangements of chromosome 3p have been found in carcinoma of renal cell and lung origin but have not been previously reported in Wilms' tumors. We present two phenotypically normal, unrelated patients with Wilms' tumors, one of which was bilateral, in which cytogenetic analysis of the tumors showed an unbalanced translocation of the p arm of chromosome 3. Two biopsies were done in the patient with bilateral Wilms' tumor. The first biopsy specimen showed a translocation between chromosome 3 and 13 with partial trisomy of 3p and loss of material from 13q. The second biopsy three and a half months later again showed trisomy of chromosome 3p. The unilateral Wilms' tumor showed trisomy of 3p with partial loss of 7p. Neither patient showed a constitutional chromosomal abnormality and neither tumor showed any cytogenetic abnormality involving chromosome 11p. Quantitative DNA analysis was performed in the tumors of both patients. The bilateral Wilms' tumor was nearly diploid with a DNA index of 1.284 (mean ploidy, 2.45; SD, 0.854) while the unilateral Wilms' tumor was aneuploid with a DNA index of 1.531 (mean ploidy, 3.35; SD, 0.976). DNA analysis results are discussed in relationship to the chromosome abnormality seen on the karyotype analysis. These cytogenetic findings suggest that genetic oncogenesis in Wilms' tumor is heterogenous.