Cytogenetic monoclonality in multifocal uroepithelial carcinomas: evidenceof intraluminal tumour seeding

Twenty-one multifocal urinary tract transitional cell carcinomas, mostly bl adder tumours, from a total of six patients were processed for cytogenetic analysis after short-term culturing of the tumour cells. Karyotypically rel ated, often identical, cytogenetically complex clones were found in all inf ormative rumours from each case, including the recurrent tumours. Rearrange ment of chromosome 9, leading to loss of material from the short and/or the long arm, was seen in all cases, indicating that this is an early, pathoge netically important event in transitional cell carcinogenesis. The presence of related clones with great karyotypic similarity in anatomically distinc t tumours from the same bladder indicates that multifocal uroepithelial tum ours have a monoclonal origin and arise via intraluminal seeding of viable cancer cells shed from the original tumour. Later lesions may develop also from cells shed from the so called second primary tumours, The relatively c omplex karyotypes seen in all lesions from most cases argue that the seedin g of tumour cells is a late event that succeeds the acquisition by them of multiple secondary genetic abnormalities.