heparin: a polysaccharide produced in basophils (especially in the lung and liver) and that inhibits the activity of thrombin in coagulation of the blood; it (trade names Lipo-Hepin and Liquaemin) is used as an anticoagulant in the treatment of thrombosis and in heart surgery
anticoagulant: medicine that prevents or retards the clotting of blood
brain tumor: a tumor in the brain