Generally stage 3 colon cancer dMMR (mismatch repair defective) is easier to treat and has a better prognosis. While pMMR (mismatch repair normal) is usually a refractory tumor with a poor outcome. dMMR, pMMR refers to the results of an immunoassay test that results in dMMR suggesting a protein deletion, while pMMR suggests no protein deletion. Protein deletions form tumor neoantigens, which are easily recognized by the body’s immune system, thus initiating an anti-tumor immune response that is more sensitive to immunotherapy. On the other hand, the absence of protein deletion will not form tumor neoantigens, which is not sensitive to immunotherapy, and is usually treated only by radiotherapy or surgery, and the efficacy is poor and prone to recurrent episodes, so pMMR tumors are not easy to treat. However, regardless of whether the immunoassay result is dMMR or pMMR, patients should be actively treated, try to improve survival, and have regular checkups.