Cancer is a general term used for a group of more than 100 diseases. Although there are many kinds of cancer, all cancers start because abnormal cells divide without control and are able to invade other tissues.

Most cancers are named for the organ or type of cell where they start. For example, cancer that begins in the breast is called breast cancer; cancer that begins in the blood (leukocytes) is called leukemia. Different types of cancer can behave differently. They grow at different rates and respond to different treatments. The main categories of cancer include:

• Carcinoma: Cancer that begins in the skin or tissues that line or cover internal organs. There are a number of subtypes of carcinoma: adenocarcinoma (e.g., breast, pancreas, lung, prostate, and colon cancers), basal cell carcinoma (usually found on areas of the body exposed to sun, most common form of cancer), squamous cell carcinoma (e.g., anal, cervical, head and neck, and vaginal cancers), and transitional cell carcinoma.
• Sarcoma: Cancer that begins in the bone, cartilage, fat, muscle, blood vessels, or other connective or supportive tissue.
• Leukemia: Cancer that starts in blood-forming tissue such as the bone marrow and causes large numbers of abnormal blood cells to be produced and enter the blood.
• Lymphoma and myeloma: Cancers that begin in the cells of the immune system.
• Central nervous system cancers: Cancers that begin in the tissues of the brain and spinal cord.

A report from the nation’s leading cancer organizations show that United States death rates from all cancers continued to fall between 2001 and 2010. Death rates for cancer are higher among the middle age and elderly population. The number of deaths was approximately 176 per 100,000 men and women per year based on the previous year’s data.

What Causes Cancer?

The body is made up of trillions of living cells. Normal body cells grow, divide, and die. Instead of dying, cancer cells continue to grow and form new, abnormal cells. Cancer cells also invade other tissues, something that normal cells cannot do. Cancer cells often travel to other parts of the body, where they begin to grow and form new tumors. This happens when cancer cells get into the body’s bloodstream or lymph vessels (the system that carries cells that help fight infections and other diseases).