Analysis by comparative genomic hybridization of epithelial and spindle cell components in sarcomatoid carcinoma and carcinosarcoma: Histogenetic aspects

Sarcomatoid carcinomas and carcinosarcomas are histologically malignant bip hasic neoplasms with an epithelial and a spindle cell component. Both a pol yclonal and a monoclonal origin have been postulated for these tumours, but the latter has been favoured. For carcinosarcoma, the stem cell from which the epithelial and mesenchymal components are derived is expected to be mo re immature than the epithelial stem cell from which different components o f sarcomatoid carcinoma originate, since in the latter, immunohistochemical or ultrastructural epithelial characteristics are still detectable, In the present study, comparative genomic hybridization was used to test the hypo thesis that both tumour components in sarcomatoid carcinoma have more chrom osomal aberrations in common than those in carcinosarcoma. From three sarco matoid carcinomas originating from the urinary bladder and two carcinosarco mas from the pharynx, the epithelial and spindle cell components were micro dissected and analysed for their respective chromosomal aberrations, using comparative genomic hybridization, High-level homology was seen in chromoso mal aberrations between the different components in each tumour. This level of homology was even higher in the carcinosarcomas (65 and 91 per cent) th an in both sarcomatoid carcinomas (21-61 per cent). The different phenotypi c components of both sarcomatoid carcinoma and carcinosarcoma show a large overlap of chromosomal aberrations, strongly suggesting a monoclonal origin for all of these tumours. These findings do not support the hypothesis tha t the divergence between epithelial and spindle cell components occurs at a n earlier stage in carcinosarcomas than in sarcomatoid carcinoma. Copyright (C) 1999 John Wiley & Sons, Ltd.