MRD: Minimal residual disease, evidence for the presence of residual malignant cells, even when so few cancer cells are present that they cannot be found by routine means. Tests for minimal residual disease (MRD) can detect some early tumors. In a patient who has been treated, the detection of MRD indicates that treatment is incomplete. MRD can thu... Found on http://www.medterms.com/script/main/art.asp?articlekey=19894