Immunohistochemical expression of DNA mismatch repair (MMR) system proteins (hMLH1, hMSH2) in cervical preinvasive and invasive lesions

Epithelial cells of CIN lesions showed a significant increase in the expression of both hMLH1 and hMSH2 proteins compared to non-neoplastic squamous epithelium (p<0.0001). The cases of invasive carcinoma showed a positivity for hMLH1 protein that was statistically lower than that for non-neoplastic cells (p=0.0009) and that for cases with CIN (p<0.0001). Positivity for hMSH2 protein was higher than that for normal epithelium (p=0.0007), but lower than that for preinvasive lesions (p=0.0001). Preinvasive lesions showed increased expression of both proteins if compared with normal esocervical epithelium. Neoplastic stromal invasiveness is associated with a significant loss of hMLH1 function.