Immunohistomorphologic and molecular cytogenetic analysis of a carcinosarcoma of the urinary bladder.

Carcinosarcomas of the urinary bladder are malignant biphasic tumors with an epithelial and a spindle cell component. For the histogenesis of the two components, a biclonal and a monoclonal origin are discussed. We present the immunomorphology and molecular cytogenetics of such a case. The immunohistology of biopsies of the urinary bladder revealed a poorly differentiated urothelial carcinoma (GIII) and a co-existing pleomorphic, spindle cell leiomyosarcoma (GIII). The two components were microdissected and further analyzed for gains and losses of chromosomal material using comparative genomic hybridization. In addition, loss of heterozygosity analyses were included. The tumor components revealed as overlapping core aberrations losses on the short arm of chromosome 9 and on the long arm of chromosome 11. However, both components showed additional aberrations exclusively detected in one of the components. The occurrence of overlapping aberrations strongly argues for a monoclonal origin of this tumor with a common ancestor. The additional aberrations of the components point to an independent and divergent course of tumor progression in both components.