Cancer, also called malignancy, is an abnormal growth of cells. There are more than 100 types of cancer, including breast cancer, skin cancer, lung cancer, colon cancer, prostate cancer, and lymphoma. Symptoms vary depending on the type. Cancer treatment may include chemotherapy, radiation, and/or surgery.
How cancer begins
Cells are the basic units that make up the human body. Cells grow and divide to make new cells as the body needs them. Usually, cells die when they get too old or damaged. Then, new cells take their place.
Cancer begins when genetic changes interfere with this orderly process. Cells start to grow uncontrollably. These cells may form a mass called a tumor. A tumor can be cancerous or benign. A cancerous tumor is malignant, meaning it can grow and spread to other parts of the body. A benign tumor means the tumor can grow but will not spread.
Some types of cancer do not form a tumor. These include leukemias, most types of lymphoma, and myeloma.
Types of cancer
Doctors divide cancer into types based on where it began. Four main types of cancer are:
Carcinomas. A carcinoma begins in the skin or the tissue that covers the surface of internal organs and glands. Carcinomas usually form solid tumors. They are the most common type of cancer. Examples of carcinomas include prostate cancer, breast cancer, lung cancer, and colorectal cancer.
Sarcomas. A sarcoma begins in the tissues that support and connect the body. A sarcoma can develop in fat, muscles, nerves, tendons, joints, blood vessels, lymph vessels, cartilage, or bone.
Leukemias. Leukemia is a cancer of the blood. Leukemia begins when healthy blood cells change and grow uncontrollably. The four main types of leukemia are acute lymphocytic leukemia, chronic lymphocytic leukemia, acute myeloid leukemia, and chronic myeloid leukemia.
Lymphomas. Lymphoma is a cancer that begins in the lymphatic system. The lymphatic system is a network of vessels and glands that help fight infection. There are two main types of lymphomas: Hodgkin lymphoma and non-Hodgkin lymphoma.
There are many other types of cancer. Learn more about these other types of cancer.
How cancer spreads
As a cancerous tumor grows, the bloodstream or lymphatic system may carry cancer cells to other parts of the body. During this process, known as metastasis, the cancer cells grow and may develop into new tumors.
One of the first places a cancer often spreads is to the lymph nodes. Lymph nodes are tiny, bean-shaped organs that help fight infection. They are located in clusters in different parts of the body, such as the neck, groin area, and under the arms.
Cancer may also spread through the bloodstream to distant parts of the body. These parts may include the bones, liver, lungs, or brain. Even if the cancer spreads, it is still named for the area where it began. For example, if breast cancer spreads to the lungs, it is called metastatic breast cancer, not lung cancer.
Watch a brief video about how cancer begins and spreads to other parts of the body.
The earlier cancer is diagnosed and treated, the better the chance of its being cured. Some types of cancer — such as those of the skin, breast, mouth, testicles, prostate, and rectum — may be detected by routine self-exam or other screening measures before the symptoms become serious. Most cases of cancer are detected and diagnosed after a tumor can be felt or when other symptoms develop. In a few cases, cancer is diagnosed incidentally as a result of evaluating or treating other medical conditions.
Cancer diagnosis begins with a thorough physical exam and a complete medical history. Laboratory studies of blood, urine, and stool can detect abnormalities that may indicate cancer. When a tumor is suspected, imaging tests such as X-rays, computed tomography (CT), magnetic resonance imaging (MRI), ultrasound, and fiber-optic endoscopy examinations help doctors determine the cancer’s location and size. To confirm the diagnosis of most cancers , a biopsy needs to be performed in which a tissue sample is removed from the suspected tumor and studied under a microscope to check for cancer cells.
If the diagnosis is positive (cancer is present), other tests are performed to provide specific information about the cancer. This essential follow-up phase of diagnosis is called staging. The most important thing doctors need to know is whether cancer has spread from one area of the body to another. If the initial diagnosis is negative for cancer and symptoms persist, further tests may be needed. If the biopsy is positive for cancer, be sure to seek a confirming opinion by a doctor who specializes in cancer treatment before any treatment is started.