Polyoma virus infection and urothelial carcinoma of the bladder following renal transplantation

Renal transplant recipients are at increased risk of bladder carcinoma. The aetiology is unknown but a polyoma virus (PV), BK virus (BKV), may play a role; urinary reactivation of this virus is common post-renal transplantation and PV large T-antigen (T-Ag) has transforming activity. In this study, we investigate the potential role of BKV in post-transplant urothelial carcinoma by immunostaining tumour tissue for PV T-Ag. There was no positivity for PV T-Ag in urothelial carcinomas from 20 non-transplant patients. Since 1990, 10 transplant recipients in our unit have developed urothelial carcinoma, and tumour tissue was available in eight recipients. Two patients were transplanted since the first case of PV nephropathy (PVN) was diagnosed in our unit in 2000 and both showed PV reactivation post-transplantation. In one of these patients, there was strong nuclear staining for PV T-Ag in tumour cells, with no staining of non-neoplastic urothelium. We conclude that PV infection is not associated with urothelial carcinoma in non-transplant patients, and is uncommon in transplant-associated tumours. Its presence in all tumour cells in one patient transplanted in the PVN era might suggest a possible role in tumorigenesis in that case.