All organs of the body are made up of cells. Normally, cells divide to produce more cells only when the body needs them. If cells keep dividing when new cells are not needed, a mass of tissue forms. This mass of extra tissue, called a growth or tumor can be benign or malignant.
Benign tumors are not cancer. They can usually be removed and, in most cases, they do not come back. Most importantly, cells from benign tumors do not spread to other parts of the body. Benign tumors are rarely a threat to life.
Malignant tumors are cancer. Cancer cells can invade and damage nearby tissues and organs. Cancer cells can also break away from a malignant tumor and enter the bloodstream or the lymphatic system. This is how cancer spreads from the original (primary) tumor to form new tumors in other parts of the body. The spread of cancer is called metastasis.
Most cancers are named for the type of cell or the organ in which they begin. When cancer spreads, the new tumor has the same kind of abnormal cells and the same name as the primary tumor. For example, if lung cancer spreads to the liver, the cancer cells in the liver are lung cancer cells. The disease is called metastatic lung cancer (it is not liver cancer).
What Causes Cancer?
Our current understanding of what causes cancer is incomplete, but it is clear that cancer is not caused by an injury, such as a bump or bruise. Being infected with certain viruses may increase the risk of some types of cancer, but cancer is not contagious. No one can "catch" cancer from another person. Cancer develops gradually as a result of a complex mix of factors related to environment, life style, and heredity. Scientists have identified many risk factors that increase the chance of getting cancer. They estimate that about 80% of all cancers are related to the use of tobacco products, to what we eat and drink, and, to a lesser extent, exposure to radiation or cancer causing agents (carcinogens) in the environment and the workplace. Some people are more sensitive than others to factors that can cause cancer.
Many risk factors can be avoided. Others, such as inherited risk factors, are unavoidable. It is helpful to be aware of them, but it is also important to keep in mind that not everyone with a particular risk factor for cancer actually gets the disease; in fact, most do not.
How Cancer Is Diagnosed?
After a physical exam, the doctor will order various tests and exams. These may include imaging procedures such as CT and MRI, which produce pictures of areas inside the body; endoscopy, which allows the doctor to look directly inside certain organs; and laboratory tests. In most cases, the doctor may order a biopsy, a procedure in which a sample of tissue is removed. A pathologist examines the tissue under a microscope to check for cancer cells.
How Is Cancer Treated?
Cancer is treated with surgery, radiation therapy, chemotherapy, hormone therapy, or biological therapy. Patients with cancer are often treated by a team of specialists, which may include a medical oncologist (specialist in medical cancer treatment), a surgeon, a radiation oncologist (specialist in radiation therapy), and others. The doctors may decide to use one treatment method or a combination of methods. The choice of treatment depends on the type and location of the cancer, the stage of the disease, the patient's age and general h