External genital abnormalities associated with Wilms tumor

The records of 170 patients with unilateral and 18 patients with bilateral Wilms tumor and 6 patients with congenital mesoblastic nephroma were reviewed for abnormalities of the external genitalia. There were 4 patients with cryptorchism, 1 with hypospadias, 1 with mixed gonadal dysgenesis, and 3 with male pseudohermaphroditism. Of the group, these 9 patients had earlier symptoms; 6 of them were under two years old. Five patients (27.7%) with bilateral Wilms tumors had external genital anomalies in contrast to only 4 (2.3%) of those with unilateral tumors. One of the 9 children with genital anomalies had unilateral congenital mesoblastic nephroma; the others had Wilms tumor. In all cases the histologic subtypes were unusual. These observations substantiate the previously reported association between external genital abnormalities and Wilms tumor and also represent a somewhat higher than expected incidence. The children with this association are remarkable for the high frequency of a particular histologic type of tumor and for the high incidence of bilaterality. The high incidence of Wilms tumors in the male pseudohermaphrodite population presented suggests that such patients should be monitored for development of renal tumors.