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 begins. Four main types of cancer are:
Carcinomas
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
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.
Leukemia
Leukemias. Leukemia is a cancer of the blood. Leukemia begins when healthy blood cells change and grow uncontrollably. The 4 main types of leukemia are acute lymphocytic leukemia, chronic lymphocytic leukemia, acute myeloid leukemia, and chronic myeloid leukemia.
Lymphomas
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 2 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, the cancer cells grow and may develop into new tumors. This is known as metastasis.
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.
Diagnosing cancer
Often, a diagnosis begins when a person visits a doctor about an unusual symptom. The doctor will talk with the person about his or her medical history and symptoms. Then the doctor will do various tests to find out the cause of these symptoms.
But many people with cancer have no symptoms. For these people, cancer is diagnosed during a medical test for another issue or condition.
Sometimes a doctor finds cancer after a screening test in an otherwise healthy person. Examples of screening tests include colonoscopy, mammography, and a Pap test. A person may need more tests to confirm or disprove the result of the screening test.
For most cancers, a biopsy is the only way to make a definite diagnosis. A biopsy is the removal of a small amount of tissue for further study. Learn more about making a diagnosis after a biopsy.
Diagnosing cancer involves a variety of tests and procedures that aim to determine the presence, location, and extent of cancer in the body. According to the National Cancer Institute, some of the most common methods used to diagnose cancer include imaging tests (such as X-rays, CT scans, MRI scans, and PET scans), laboratory tests (such as blood tests and urine tests), and biopsies . Biopsies are considered the most definitive method of diagnosing cancer, as they involve the removal of a sample of tissue or fluid from the body for examination under a microscope
The specific diagnostic tests and procedures used for cancer diagnosis can vary depending on the type and location of the cancer, as well as the individual patient's symptoms and medical history. For example, a mammogram may be used to diagnose breast cancer, while a colonoscopy may be used to diagnose colon cancer .
It is important to note that a cancer diagnosis can be a complex and emotionally challenging process. Patients and their loved ones may benefit from seeking support from healthcare providers, support groups, or mental health professionals .
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