Mismatch repair deficiency and its relationship with histopathological features in gastric cancer patients.

Gastric cancer is a common malignancy disease with a poor prognosis. Deficient mismatch repair is a prognostic and predictive marker of response to systemic therapies. However, deficient mismatch repair frequency and the relationship between this status and microscopic characteristics are inconsistent across nations. We aimed to determine the rate of deficient mismatch repair and its association with histopathological features in gastric cancer patients. A cross-sectional study was conducted on 226 gastric cancer patients treated at Hue University of Medicine and Pharmacy Hospital and Hue Central Hospital from June 2020 to January 2024. Mismatch repair protein expression was evaluated using immunohistochemical staining, and any absence of mismatch repair proteins was regarded as deficient mismatch repair. The deficient mismatch repair rate was 12.8%. Deficient mismatch repair appeared to be more frequent in the intestinal subtype of Lauren classification odds ratio (OR) = 4.767 (95% confidence interval [CI], 1.086-20.921; p = 0.039), tubular/papillary adenocarcinoma (OR = 5.25; 95% CI, 1.185-23.251; p = 0.029), mucinous adenocarcinoma (OR = 6.19; 95% CI, 1.113-34.445; p = 0.037), and differentiated type (OR = 3.24; 95% CI, 1.324-7.931; p = 0.01). No statistically significant association was detected with histopathological features according to the Tumor Location-Modified Lauren classification and mucinous secreting morphology. Deficient mismatch repair status was unusual in gastric cancer. The degree of cell differentiation and microscopic characteristics based on the World Health Organization and Lauren classification could all impact the predictive power for microsatellite-instable status.