Loss of DNA-mismatch repair gene expression in oral melanomas

The defect of DNA mismatch repair is postulated to be responsible for malig nant transformation in many types of rumours. The main aim of this study wa s to evaluate the expression of DNA mismatch repair proteins in 29 cases of oral melanomas and to relate this to the ploidy status of the lesions. MLH 1 expression was found in 4/29, MSH2 in 6/29, PMS2 in 2/29 and PMS1 in 0/29 cases investigated. The range of positively stained cells did not exceed 5 0% with MSH2, and PMS2, or 55 with MLH1. Loss of the DNA mismatch repair ge ne expression correlated with high aneuploidy ratio, observed in totally ne gative cases.