Positive MLH1 means that MLH1 is normal and the body’s risk of developing malignant tumors is less than that of MLH1 negative. MLH1 belongs to a type of immunohistochemistry test, which is clinically referenced to whether or not one is suffering from gastric cancer, colon cancer, rectal cancer, endometrial cancer, lung cancer and other diseases. If MLH1 negative means mismatch repair is missing, the risk of cancer is higher than MLH1 positive. MLH1 positivity alone only indicates that the body is at a lower risk of developing these malignant neoplastic diseases, and the specific diagnosis needs to be confirmed by combining clinical symptoms, as well as the results of tissue biopsy and ancillary tests. Once malignant neoplastic diseases are diagnosed, appropriate interventions should be taken as soon as possible to detect and treat the disease early, which will help recovery.