Abstract: Objective To investigate the correlation between microsatellite instability (MSI) and human epidermal growth factor receptor 2 (HER-2) expression with its malignancy in colorectal cancer, and the clinical application value of the combination of MSI and HER-2 in colorectal cancer. Methods A retrospective analysis was performed on the clinical data of 425 colorectal cancer patients who did not receive any form of adjuvant therapy before the treatment of gastrointestinal surgery in the Second Affiliated Hospital of Dalian Medical University. Statistical analysis was carried out to analyze the correlation between MSI and HER2 expression with its clinical data. Results The high expression of HER2 in colorectal cancer was related to the degree of tumor differentiation and depth of invasion (P＜0.05). MSI-H and MSS/MSI-L were related to tumor size. There were differences in the site, differentiation, tissue type, depth of invasion, anemia, and CA199 expression (P＜0.05). There was a correlation between MSI and HER2 expression. Conclusions HER2 and MSI have certain synergy effects in evaluating the degree of malignancy of colorectal cancer. The combined detection of these two factors could have an important guiding role in the assessment of malignancy of colorectal cancer.

Key words: Keywords: colorectal cancer, degree of malignancy, MSI, HER2