On the origin of syn- and metachronous urothelial carcinomas.

OBJECTIVE To evaluate existing models for the origin of meta- and synchronous urothelial carcinomas in light of the accumulated genetic data. METHODS Published studies on the clonal origin and genetic relationships of syn- and metachronous tumors, genetic aberrations in normal and premalignant urothelial lesions, as well as histologic and genetic mapping studies of cystectomized bladder samples are reviewed. RESULTS The most common models for the origin of syn- and metachronous tumors are found to conform less well to the accumulated genetic data. A new model is proposed, the field-first-tumor-later model, in which aberrant cells with a stem cell, or stem cell-like, origin spread in the urothelium by cellular displacement, creating fields of premalignant cells. Tumor growth is suggested to be initiated by critical genetic events occurring in individual cells in such fields. Hence, recurring tumors are proposed to originate from a shared field of premalignant cells and not from previous overt tumors. CONCLUSIONS The proposed model can better account for the existing genetic and histological data on syn- and metachronous urothelial carcinomas.