Negative hMSH2 protein expression in pancreatic carcinoma may predict a better prognosis of patients

The prognostic values of immunohistochemical staining for hMSH2 and hMLH1 in patients with pancreatic carcinomas were investigated. Fifty-five patients with histologically proven pancreatic carcinomas were studied. Immunohistochemical staining for hMSH2 and hMLH1 was performed by avidin-biotin-peroxidase complex method with a catalyzed signal amplification system. Tumor cells that exhibited an absence of nuclear staining in the presence of non-neoplastic cells with nuclear staining were considered to have an abnormal pattern. Four tumors (7.3%) demonstrated abnormal hMS2-negative staining. One tumor (1.8%) had abnormal hMLH1-negative staining and this tumor showed negative hMSH2 staining. No particular clinicopathologic factor such as tumor location, histology, T-factor, N-factor and TNM-stage were observed in patients with negative hMSH2 staining tumors. Median survival time (MST) of patients with hMSH2-negative tumors was comparatively longer than that of patients with hMSH2-positive tumors, however, there was no significant difference between MSTs of the two groups (56 months vs. 14 months; p=0.16). We concluded that negative hMSH2 immunohistochemical staining in the pancreatic carcinomas may demonstrate certain patients, but not all, who had microsatellite instability-positive tumors. The patients with hMSH2-negative tumors may have better prognoses than those with hMSH2-positive tumors. To clarify these findings, further large number of pancreatic carcinomas must be investigated.