NCI says tumor angiogenesis starts with cancerous tumor cells releasing molecules that send signals to activate genes in the host tissue that, in turn, make proteins to encourage growth of new blood vessels. Certain molecules can either activate or inhibit angiogenesis. Studies are now examining the effectiveness of drugs aimed at inhibiting angiogenesis in specific cancers. Types of cancer Cancer can begin in any part of the body, and is categorized by the type of tissue where it starts. Carcinomas, according to NCI, are the most common types of cancer.
Carcinomas start in cells that cover external and internal body surfaces.
Lung, breast, and colon cancer are the most frequent cancers of this type in the United States. Sarcomas start in cells found in the supporting tissues of the body such as bone, cartilage, fat, connective tissue, and muscle. Lymphomas begin in the lymph nodes and tissues of the body's immune system. Leukemias are cancers of the immature blood cells that grow in the bone marrow and can accumulate in large numbers in the bloodstream. A carcinogen is a substance that can cause cancer.