The term cancer collectively refers to more than 100 different diseases that affect nearly every part of the body. Throughout our lives, healthy cells in the body divide, grow, and replace themselves in a controlled fashion. Cancer starts when the genes directing this cellular division malfunction and cells begin to multiply and grow out of control. A mass or clump of these abnormal cells is called a tumor. Not all tumors, however, are cancerous. Benign tumors, such as moles, stop growing and do not spread to other parts of the body. But cancerous, or malignant, tumors continue to grow, crowding out healthy cells, interfering with body functions and drawing nutrients away from body tissues. These malignant tumors can spread to other parts of the body through a process called metastasis. Cells from the original tumor break off, travel through the blood or lymphatic vessels and eventually form new tumors elsewhere in the body. Only 5 to 10% of cancers are thought to be hereditary. The rest of the time, the genetic mutation that leads to the disease is brought on by other factors. The most common cancers are linked to smoking, sun exposure, and diet. These factors, combined with your age, family history, and overall health, contribute to your cancer risk.

Whether a specific complaint led you to seek medical care or your doctor noticed something unusual during a routine check-up, chances are you have had or will soon undergo a biopsy, the extraction and examination of a small amount of suspect tissue, to confirm that you do indeed have cancer. The earlier your cancer is diagnosed and treatment begun, the better your chances of making a full recovery. Depending on the type of cancer you have, a cancer specialist, called an oncologist, may recommend surgery, radiation, chemotherapy, or some combination.

Surgery is meant to remove well-defined tumors - a cancerous lump in the breast or colon, for example. The surgeon will remove the tumor and if tests indicate that the cancer has not spread, surgery may be the only treatment required. The goal of chemotherapy, or "drug or chemical therapy", is destruction of any cancer cells that may have split off from the original tumor and threaten to take hold elsewhere. The drugs you will receive depend on which type of cancer you have. In radiation, also called radiotherapy, a cell-destroying X-ray beam is aimed directly at the cancerous area.