Tumor biomarkers are substances that can be measured in blood, tissues, or other bodily fluids that indicate the presence of a tumor or provide information about the tumor's characteristics. These biomarkers can help in the early detection, diagnosis, and monitoring of cancer, as well as in predicting a patient's response to treatment and prognosis. Tumor biomarkers can include proteins, genes, hormones, enzymes, or other molecules that are specific to cancer cells or are produced by the body in response to the presence of a tumor. Research in this area aims to identify and validate new tumor biomarkers, develop diagnostic tests based on these biomarkers, and improve the personalized treatment of cancer patients based on their biomarker profile.