Lower incidence of urothelial cell carcinoma due to the concept of a clonal origin

Synchronous and metachronous tumours are frequently observed in the urinary tract and may he explained by the concept of 'field cancerisation',ie. exp osure to carcinogens leads to independent transformation of many urothelial cells resulting in genetically unrelated tumours. However, increasing evid ence supports the concept of clonality, i.e. the progeny of a single transf ormed cell spreads through the urinary system resulting in genetically rela ted tumours. The aim of this study was to review the molecular biological e vidence for both concepts and to assess the consequences of a clonality ass umption on the incidence of urothelial cell carcinoma (UCC). In total 1198 non-invasive and 1113 invasive (greater than or equal to T1) UCCs of the bl adder were registered as incident tumours in 1996-1997 by three Dutch cance r registries following the current registration rules of the International Association of Cancer Registries (IACR). Assuming clonality, the number of mon-invasive and invasive bladder UCCs decreased by 10.9% and 11.5% respect ively. A decline of 8.5% and 9.5% was found for UCCs of the ureter and rena l pelvis, respectively. Current registration rules have substantial impact on the incidence estimates of UCC. New insights into the molecular biology of UCC should be translated into registration rules. (C) 2000 Elsevier Scie nce Ltd. All rights reserved.