The value of D-dimer is elevated to some extent when a tumor develops, but an elevated D-dimer alone is not proof of tumorigenesis. D-dimer is a degradation product of human fibrin, which is often used to reflect the activity of human fibrinolytic system. When the tumor occurs, often combined with the production of a large number of procoagulant substances, so it is easy to form blood coagulation or thrombosis, at this time the body’s fibrinolytic system is activated, producing a large number of fibrinolytic products, then the D-dimer test value is elevated. However, the elevation of D-dimer is not necessarily caused by tumor, when diffuse intravascular coagulation, pulmonary thromboembolism and other diseases occur, the measurement value of D-dimer will also be elevated to a certain extent. Therefore, the definitive diagnosis of a tumor requires a combination of clinical and other ancillary test results.