Metachronous multifocal development of urothelial cancers by intraluminal seeding.

To investigate the clonal origin of multifocal urothelial tumours, we analysed the p53 tumour-suppressor gene in 3 cases with bladder tumours developing after treatment for a renal pelvic or ureteral tumour and in 1 case with a ureteral tumour after treatment for a bladder tumour. For each case, identical p53 gene mutations were detected in all primary and recurrent tumours. The results suggest that heterotopic recurrence by intraluminal seeding from the original tumour is common in urothelial cancer. The data also support the view that multifocal urothelial tumours are derived from a single progenitor cell.