Expression of mismatch repair proteins in invasive and in situ carcinoma of the breast.

BACKGROUND Genetic instability is a characteristic feature of familial and sporadic breast carcinomas. It is not clear whether defects in the mismatch repair system accompany this instability. The purpose of this study was to explore the expression of two of the proteins encoded by the DNA mismatch repair genes, namely MLH1 and MSH2, in sporadic in situ and invasive breast carcinomas of various types and grades occurring in Greek patients. MATERIALS AND METHODS MLH1 and MSH2 expression was monitored immunohistochemically in 60 breast carcinomas (20 in situ and 40 invasive). RESULTS-CONCLUSION: Although we did not detect loss of MLH1 or MSH2 expression, we do believe that our data will contribute to a better understanding of the role of the mismatch repair (MMR) system in breast cancer.