A type of tumor that forms from cells that make blood vessels or lymph vessels. Vascular tumors may be benign (not cancer) or malignant (cancer) and can occur anywhere in the body. They may form on the skin, in the tissues below the skin, and/or in an organ. There are many types of vascular tumors. The most common type of vascular tumor is hemangioma, which is a benign tumor that usually occurs in infants and goes away on its own.