Cytogenetic evidence of gene amplification in urothelial cancer--a possible mechanism of tumor invasiveness.

A cytogenetically detectable form of gene amplification, presumably oncogene amplification, double minute chromosomes, has been found in 11 out of 45 specimens (24%) of moderately and poorly differentiated, deeply infiltrating transitional cell carcinoma of the bladder and ureter. None of the 75 low-grade low-stage tumors contained this karyotypic anomaly. It is obvious that double minutes are not a rare and sporadic phenomenon in this type of tumors; additionally there is strong evidence that they are involved in tumor progression, i.e. they are associated with tumor aggressiveness and unfavorable prognosis.