MSI-High/dMMR Tumors (e.g., Colon, Endometrial, Stomach Cancer)

Microsatellite Instability-High (MSI-High) and mismatch repair-deficient (dMMR) tumours arise when the body's intrinsic DNA repair mechanisms malfunction, resulting in genetic aberrations during cellular division. These anomalies are most frequently observed in colorectal, endometrial, and gastric malignancies and may be either hereditary (as in Lynch syndrome) or acquired.

MSI-High/dMMR tumours typically contain numerous mutations that produce abnormal proteins, which the immune system recognises as foreign. Because of this trait, they are especially sensitive to immune checkpoint inhibitors like pembrolizumab and nivolumab, which help the immune system fight cancer cells better.

For colorectal cancer, testing for MSI/dMMR status is now a common element of diagnosis. It helps doctors decide on treatment and make predictions about the disease's course. In endometrial cancer, it can assist in finding inherited cancer syndromes and affect treatment decisions. In stomach cancer, it suggests a higher probability of efficacy with immunotherapy.

Finding out early that someone has MSI-High/dMMR status not only makes therapy more accurate, but it also lets family members who may be at a higher risk of cancer get genetic counselling. This method makes sure that the cancer care plan is more focused, effective, and tailored to each patient.