대한대장항문학회

Purpose: DNA replication errors (RERs) in repeated nucleotide sequences (microsatellite instability) is caused by defective mismatch repair (MMR) genes. Ninety percent of colorectal carcinomas in hereditary nonpolyposis colorectal cancer (HNPCC)<br>patients and 10∼15% of sporadic colorectal cancers show microsatellite instability. In the majority of colorectal cancers with microsatellite instability, the defective MMR gene is hMLH1 or hMSH2. The author examined immunohistochemical<br>expression<br>of<br>hMLH1 and hMSH2 in 75 cases of colorectal carcinomas excluding HNPCC, based on Amsterdam criteria for investigating clinicopathological characteristics and prognosis in hMLH1/hMSH2 negative cases.<br>Methods: Formalin fixed, paraffin blocks obtained from tumors of 75 cases of colorectal cancers were stained with two monoclonal antibodies (hMLH1 and hMSH2). The correlation between hMLH1/hMSH2 negativity, and clinicopathological feature and<br>prognosis<br>were statistically analysed.<br>Results: Twelve cases (16.0%) showed hMLH1/hMSH2 negativity. Negative expression of hMLH1/hMSH2 was associated with early onset (under age 50), proximal location, multiplicity, mucinous histologic type and poor differentiation. There was a<br>significant<br>survival advantage in patients with hMLH1/hMSH2 negative colorectal carcinoma.<br>Conclusions: This study shows that hMLH1/hMSH2 negative colorectal carcinomas have the same clinicopathological characteristics of colorectal carcinomas with microsatellite instability. The immunohistochemical test for hMLH1/hMSH2 protein can be<br>a<br>simple screening method routinely applicable. The result of this test is available for establishing guidelines for management, and an independent prognostic factor for sporadic colorectal cancers.<br>