Characteristics of MMR protein expression in colorectal cancer and MMR gene variations in Vietnamese patients with Lynch syndrome

Abstract Objectives Detecting and diagnosing Lynch syndrome in colorectal cancer patients is essential for enhancing the quality of diagnosis, treatment, and management. This study aims to characterize mismatch repair (MMR) protein expression and MMR gene variants in Vietnamese patients. Methods A total of 218 patients diagnosed with colorectal cancer at the Nuclear Medicine and Oncology Center, Bach Mai Hospital (Hanoi, Vietnam) were included in this descriptive, retrospective study. Tumor tissue samples were evaluated for MMR protein expression. Cases with loss of MMR protein expression underwent genomic sequencing for MMR gene mutations. Results Among 218 colorectal cancer patients, 135 were men (61.9 %) and 83 were women (38.1 %), aged 16–86 years. The prevalence of MMR deficiency (dMMR) was 14.7 %. The expression loss rates of the MLH1, MSH2, MSH6, PMS2, MLH1/PMS2, and MSH2/MSH6 proteins were 9.4 %, 3.1 %, 3.1 %, 21.9 %, 46.9 %, and 15.6 %, respectively. Within the dMMR group, four variants were identified in the MLH1 gene, one in the MSH2 gene, two in the PMS2 gene, and one in the EPCAM gene, and all were classified as germline pathogenic variants associated with Lynch syndrome. Conclusion This is a study to apply next-generation sequencing (NGS) technology to diagnose Lynch syndrome from dMMR cases in Vietnamese colorectal cancer patients. Our research supports the screening and diagnosis of Lynch syndrome through testing using MMR protein expression and assessing pathogenic variants in MMR genes.