Definition

Describes cells that have mutations (changes) in certain genes that are involved in correcting mistakes made when DNA is copied in a cell. dMMR cells usually have many DNA mutations, which may lead to cancer. dMMR is most common in colorectal cancer, other types of gastrointestinal cancer, and endometrial cancer, but it may also be found in cancers of the breast, prostate, bladder, and thyroid and in an inherited disorder called Lynch syndrome. Knowing if a tumor is dMMR may help plan treatment or predict how well the tumor will respond to treatment. Also called deficient DNA mismatch repair, deficient mismatch repair, mismatch repair deficiency, and MMR deficiency.