The article discusses the role of microsatellite instability (MSI) in colorectal cancer (CRC). MSI is a condition where microsatellite sequences (MS) differ between normal and cancer cells, indicating genomic instability. MSI is caused by a damaged mismatch repair mechanism (MMR), primarily involving the proteins MSH2, MLH1, and MSH6. MSI-H, a more severe form of MSI, is present in 15% of CRC cases and is associated with poor prognosis and chemoresistance. The article highlights that MSI-H is an important prognostic factor and a predictive factor for chemotherapeutic treatment efficacy. Clinical trials have shown contradictory results regarding the effectiveness of chemotherapy in MSI-H patients, particularly with 5-fluorouracil (5-FU). However, MSI-H patients have shown better survival rates in some studies. The article concludes that MSI-H is a significant factor in CRC management and future research should focus on individualized therapy based on molecular characteristics, such as MSI-H, to improve treatment outcomes.The article discusses the role of microsatellite instability (MSI) in colorectal cancer (CRC). MSI is a condition where microsatellite sequences (MS) differ between normal and cancer cells, indicating genomic instability. MSI is caused by a damaged mismatch repair mechanism (MMR), primarily involving the proteins MSH2, MLH1, and MSH6. MSI-H, a more severe form of MSI, is present in 15% of CRC cases and is associated with poor prognosis and chemoresistance. The article highlights that MSI-H is an important prognostic factor and a predictive factor for chemotherapeutic treatment efficacy. Clinical trials have shown contradictory results regarding the effectiveness of chemotherapy in MSI-H patients, particularly with 5-fluorouracil (5-FU). However, MSI-H patients have shown better survival rates in some studies. The article concludes that MSI-H is a significant factor in CRC management and future research should focus on individualized therapy based on molecular characteristics, such as MSI-H, to improve treatment outcomes.