Cancer is the uncontrolled growth of abnormal cells in the body. Cancerous cells are also called malignant cells.
Cancer is made of cells in the body. Normal cells multiply when the body needs them, and die when they are damaged or the body doesn't need them.
Cancer occurs when the genetic material of a cell becomes changed. This results in cells growing out of control. Cells divide too quickly and do not die in a normal way.
There are many kinds of cancer. Cancer can develop in almost any organ or tissue, such as the lung, colon, breast, skin, bones, or nerve tissue.
There are many risk factors for cancer, including:
Smoking tobacco or other substances
Chewing tobacco
Benzene and other chemical exposures
Drinking too much
Environmental toxins, such as certain poisonous mushrooms and a type of mold that can grow on peanut plants and produce a toxin called
Genetic problems
Obesity
Radiation exposure
Too much sunlight exposure
Viruses
The cause of many cancers remains unknown.
The most common cause of cancer-related death is lung cancer.
In the United States, skin cancer followed by breast cancer are the most commonly diagnosed cancers.
In US men, other than skin cancer, the three most common cancers are:
In US women, other than skin cancer, the three most common cancers are:
Lung cancer
Colorectal cancer
Some cancers are more common in certain parts of the world. For example, in Japan, there are many cases of
. But in the United States this type of cancer is much less common. Differences in diet or environmental factors may play a role.
Some other types of cancer include:
Symptoms of cancer depend on the type and location of the cancer. For example, lung cancer can cause coughing, shortness of breath, or chest pain. Colon cancer may cause diarrhea, constipation, or blood in the stool.
Some cancers may not have any symptoms. In certain cancers, such as pancreatic cancer, symptoms often do not start until the disease has reached an advanced stage.
The following symptoms may occur with cancer:
Chills
Fatigue
Fever
Loss of appetite
Night sweats
Pain
Weight loss
Like symptoms, the signs of cancer vary based on the type and location of the
. Common tests include the following:
of the tumor
Blood tests (which look for chemicals called tumor markers that can be elevated or abnormal with certain types of cancer)
(for lymphoma or leukemia)
(CBC)
Most cancers are diagnosed by biopsy. Depending on the location of the tumor, the biopsy may be a simple procedure or a serious operation. Most people with cancer have CT scans to determine the exact location and size of the tumor or tumors.
A cancer diagnosis is often difficult to cope with. It is important that you discuss the type, size, and location of the cancer with your health care provider when you are diagnosed. You also will want to ask about treatment options, along with the prognosis (likely outcome), benefits, and risks.
It's a good idea to have someone with you at the provider's office to help you get through and understand the diagnosis. If you have trouble asking questions after hearing about your diagnosis, the person you bring with you can ask them for you.
The treatment varies, based on the type of cancer and its stage. The stage of a cancer refers to how much it has grown and whether the cancer has spread from its original location.
If the cancer is in one location and has not spread, the most common treatment approach is surgery to cure it. This is often the case with skin cancers, as well as cancers of the lung, breast, and colon.
If the cancer has spread to local lymph nodes only, sometimes these can also be removed with the cancer.
If surgery cannot remove all of the cancer, the options for treatment may include
,
,
,
, or other types of treatment. Some cancers require a combination of treatments. Lymphoma, or cancer of the lymph glands, is rarely treated with surgery. Chemotherapy, immunotherapy, radiation therapy, and other nonsurgical therapies are often used.
Although treatment for cancer can be difficult, there are many ways to keep up your strength.
If you have radiation treatment:
Treatment is usually scheduled every weekday.
You should allow 30 minutes for each treatment session, although the treatment itself usually takes only a few minutes.
You should get plenty of rest and eat a well-balanced diet during the course of your radiation therapy.
Skin in the treated area may become sensitive and easily irritated.
Some side effects of radiation treatment are temporary. They vary, depending on the area of the body that is being treated.
If you have chemotherapy:
Eat well.
Get plenty of rest, and don't feel like you have to accomplish tasks all at once.
Avoid people with colds, the flu,
, or any other infectious illness. Chemotherapy can cause your immune system to weaken.
Talk with family, friends, or a support group about your feelings. Work with your providers throughout your treatment. Helping yourself can make you feel more in control.
The diagnosis and treatment of cancer often causes a lot of anxiety and can affect a person's entire life. There are many
for people with cancer.
The outlook depends on the type of cancer and the stage of the cancer when diagnosed.
Some cancers can be cured. Other cancers that are not curable can still be treated effectively. Some people can live for many years with cancer. Other cancers are quickly life threatening.
Complications depend on the type and stage of cancer. The cancer may spread.
Contact your provider if you develop symptoms of cancer.
You can reduce the risk of getting a cancerous (malignant) tumor by:
Eating healthy foods
Exercising regularly
Limiting alcohol use
Maintaining a healthy weight
Minimizing your exposure to radiation and toxic chemicals
or chewing tobacco
Reducing sun exposure, especially if you burn easily
Cancer screenings, such as
for breast cancer and stool blood testing or
for colon cancer, may help catch these cancers at their early stages when they are most treatable. This is particularly valuable in people with a family history of cancer. Some people at high risk for developing certain cancers can take medicines to reduce their risk.
Carcinoma; Malignant tumor
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National Cancer Institute website. Chemotherapy and you: support for people with cancer.
www.cancer.gov/publications/patient-education/chemo-and-you
. Updated January 2024. Accessed December 30, 2024.
National Cancer Institute website. Radiation therapy and you: support for people with cancer.
www.cancer.gov/publications/patient-education/radiation-therapy-and-you
. Updated April 2021. Accessed December 30, 2024.
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.
Updated by: Frank D. Brodkey, MD, FCCM, Associate Professor, Section of Pulmonary and Critical Care Medicine, University of Wisconsin School of Medicine and Public Health, Madison, WI. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.