molecular marker

Definition of molecular marker
National Cancer Institute

molecular marker

(muh-LEH-kyoo-ler MAR-ker)
A biological molecule found in blood, other body fluids, or tissues that is a sign of a normal or abnormal process, or of a condition or disease. A molecular marker may be used to see how well the body responds to a treatment for a disease or condition. Also called biomarker and signature molecule.

Source: NCI Dictionary of Cancer Terms