How cancer starts

It's likely that this varies among cancer types. While doctors have an idea of what may increase your risk of cancer, the majority of cancers occur in people who don't have any known risk factors. Factors known to increase your risk of cancer include:. Cancer can take decades to develop. That's why most people diagnosed with cancer are 65 or older.

While it's more common in older adults, cancer isn't exclusively an adult disease — cancer can be diagnosed at any age. Certain lifestyle choices are known to increase your risk of cancer. Smoking, drinking more than one drink a day for women and up to two drinks a day for men, excessive exposure to the sun or frequent blistering sunburns, being obese, and having unsafe sex can contribute to cancer. You can change these habits to lower your risk of cancer — though some habits are easier to change than others.

Only a small portion of cancers are due to an inherited condition. If cancer is common in your family, it's possible that mutations are being passed from one generation to the next. You might be a candidate for genetic testing to see whether you have inherited mutations that might increase your risk of certain cancers.

Keep in mind that having an inherited genetic mutation doesn't necessarily mean you'll get cancer. Some chronic health conditions, such as ulcerative colitis, can markedly increase your risk of developing certain cancers. Talk to your doctor about your risk.

The environment around you may contain harmful chemicals that can increase your risk of cancer. Even if you don't smoke, you might inhale secondhand smoke if you go where people are smoking or if you live with someone who smokes.

Chemicals in your home or workplace, such as asbestos and benzene, also are associated with an increased risk of cancer. Cancer care at Mayo Clinic. Mayo Clinic does not endorse companies or products. Advertising revenue supports our not-for-profit mission. This content does not have an English version.

This content does not have an Arabic version. 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. Request Permissions. What is Cancer? Approved by the Cancer. How cancer begins Cells are the basic units that make up the human body. Types of cancer Doctors divide cancer into types based on where it begins. There are four common types of leukemia, which are grouped based on how quickly the disease gets worse acute or chronic and on the type of blood cell the cancer starts in lymphoblastic or myeloid.

Acute forms of leukemia grow quickly and chronic forms grow more slowly. Our page on leukemia has more information. Lymphoma is cancer that begins in lymphocytes T cells or B cells. These are disease-fighting white blood cells that are part of the immune system.

In lymphoma, abnormal lymphocytes build up in lymph nodes and lymph vessels, as well as in other organs of the body. Hodgkin lymphoma — People with this disease have abnormal lymphocytes that are called Reed-Sternberg cells. These cells usually form from B cells. Non-Hodgkin lymphoma — This is a large group of cancers that start in lymphocytes. The cancers can grow quickly or slowly and can form from B cells or T cells. Our page on lymphoma has more information.

Multiple myeloma is cancer that begins in plasma cells , another type of immune cell. The abnormal plasma cells, called myeloma cells, build up in the bone marrow and form tumors in bones all through the body. Multiple myeloma is also called plasma cell myeloma and Kahler disease. Our page on multiple myeloma and other plasma cell neoplasms has more information. Melanoma is cancer that begins in cells that become melanocytes, which are specialized cells that make melanin the pigment that gives skin its color.

Most melanomas form on the skin, but melanomas can also form in other pigmented tissues, such as the eye. Our pages on skin cancer and intraocular melanoma have more information. There are different types of brain and spinal cord tumors. These tumors are named based on the type of cell in which they formed and where the tumor first formed in the central nervous system. For example, an astrocytic tumor begins in star-shaped brain cells called astrocytes , which help keep nerve cells healthy.

Brain tumors can be benign not cancer or malignant cancer. Our pages on brain and spinal cord tumors in adults and brain and spinal cord tumors in children have more information.

Germ cell tumors are a type of tumor that begins in the cells that give rise to sperm or eggs. These tumors can occur almost anywhere in the body and can be either benign or malignant. Neuroendocrine tumors form from cells that release hormones into the blood in response to a signal from the nervous system. These tumors, which may make higher-than-normal amounts of hormones, can cause many different symptoms.

Neuroendocrine tumors may be benign or malignant. Our definition of neuroendocrine tumors has more information. Carcinoid tumors are a type of neuroendocrine tumor. They are slow-growing tumors that are usually found in the gastrointestinal system most often in the rectum and small intestine. Carcinoid tumors may spread to the liver or other sites in the body, and they may secrete substances such as serotonin or prostaglandins, causing carcinoid syndrome.

Our page on gastrointestinal carcinoid tumors has more information. Menu Contact Dictionary Search. Understanding Cancer.

What Is Cancer? Cancer Statistics. Cancer Disparities. Cancer Causes and Prevention. Risk Factors. Cancer Prevention Overview. Cancer Screening Overview. Screening Tests. Diagnosis and Staging. Questions to Ask about Your Diagnosis. Types of Cancer Treatment.

Side Effects of Cancer Treatment. Clinical Trials Information. A to Z List of Cancer Drugs. Questions to Ask about Your Treatment.

Feelings and Cancer. Adjusting to Cancer. Day-to-Day Life. Support for Caregivers. Questions to Ask About Cancer. Choices for Care. Talking about Your Advanced Cancer. Planning for Advanced Cancer. Advanced Cancer and Caregivers.

Questions to Ask about Advanced Cancer. When a kid has these problems, it's often caused by something less serious, like an infection. With medical testing, the doctor can figure out what's causing the trouble.

If the doctor suspects cancer, he or she can do tests to figure out if that's the problem. A doctor might order X-rays and blood tests and recommend the person go to see an oncologist say: on-KAH-luh-jist. An oncologist is a doctor who takes care of and treats cancer patients.

The oncologist will likely run other tests to find out if someone really has cancer. If so, tests can determine what kind of cancer it is and if it has spread to other parts of the body. Based on the results, the doctor will decide the best way to treat it.

One test that an oncologist or a surgeon may perform is a biopsy say: BY-op-see. During a biopsy, a piece of tissue is removed from a tumor or a place in the body where cancer is suspected, like the bone marrow.

Don't worry — someone getting this test will get special medicine to keep him or her comfortable during the biopsy. The sample that's collected will be examined under a microscope for cancer cells. The sooner cancer is found and treatment begins, the better someone's chances are for a full recovery and cure. Cancer is treated with surgery, chemotherapy, or radiation — or sometimes a combination of these treatments. The choice of treatment depends on:.

Surgery is the oldest form of treatment for cancer — 3 out of every 5 people with cancer will have an operation to remove it. During surgery, the doctor tries to take out as many cancer cells as possible. Some healthy cells or tissue may also be removed to make sure that all the cancer is gone.

Chemotherapy say: kee-mo-THER-uh-pee is the use of anti-cancer medicines drugs to treat cancer. These medicines are sometimes taken as a pill, but usually are given through a special intravenous say: in-truh-VEE-nus line, also called an IV. An IV is a tiny plastic catheter straw-like tube that is put into a vein through someone's skin, usually on the arm.