Bilateral Wilms' tumour. Age at diagnosis, associated congenital anormalies, and possible pattern of inheritance.

A series of 87 patients with Wilms' tumour seen during the period 1960-73 included 11 (13%) with bilateral tumours. 6 patients presented with simultaneous bilateral tumours, 2 had tumours in each side of a horseshoe kidney, and 3 later developed a tumour in the remaining kidney. There was no reported familial incidence of Wilms' tumour. Maternal age at birth of the patients with simultaneous bilateral tumours was over 30 years in 7/8 cases. The average of patients with bilateral tumours was 15 months, whereas that of patients with unilateral tumours was 31/2 years. All the simultaneously occurring bilateral tumours and those within a horseshoe kidney were multifocal, whilst the sequentially occurring bilateral tumours and the unilateral tumours all developed as a single tumour mass within the affected kidney. Associated congenital anomalies were found in 5 (45%) of 11 patients with bilateral tumours, several of whom had more than one defect. Of 76 patients with a unilateral tumour, only 3 (4%) had congenital anomalies.