What causes cancer?

Cancer occurs when old cells do not die when they should or are damaged. Normally, the body repairs or destroys such cells. Sometimes, these cells may grow out of control. This causes growths or tumors to form. Tumors can be benign (not cancer) or malignant (cancer).

Benign tumors do not spread to other parts of the body. Malignant tumors can invade and destroy healthy tissues and organs. Cancer cells also can spread to other parts of the body and form new tumors.

The risk of cancer can be inherited in a person’s genes. In some cases, cancer can be caused by being exposed to a harmful substance such as a virus, certain chemicals, or radiation. Sometimes more than one cause is involved.

What types of cancer are most likely to occur in women?

In women, cancer is most likely to occur in the following areas:

What are the warning signs of cancer?

Most types of cancer have early warning signs that something is wrong. If you notice any of these signs, contact your health care provider right away:

  • A change in bowel or bladder habits
  • A sore that does not heal
  • Unusual bleeding or discharge
  • Thickening or a lump in the breast or other parts of the body
  • Indigestion or difficulty swallowing
  • A change in a wart or mole
  • A nagging cough or hoarseness

Data from the American Cancer Society. Signs and symptoms of cancer. ACS: 2005.

None of these signs is a sure sign of cancer. They are clues that something could be wrong. If you notice any of these signs, see your doctor right away. Getting treatment early increases your chances of successful treatment, whether you have cancer or some other problem.

Click on the FAQs below to expand

Are there screening tests for cancer?

There are screening tests for some forms of cancer, including breast cancer, cancer of the cervix, and colorectal cancer. These tests should be a part of your routine health care. They help find changes in the body that may be early signs of cancer or may lead to cancer.

When should I have cancer screening tests?

This table shows routine screening tests that all women should have. Based on your risk factors for certain types of cancer, your doctor may recommend additional tests or exams or having them more often.

Cancer Screening Tests
Type of Cancer Test or Exam Who Should Be Screened When
Breast Mammography Women aged 40 years and older Yearly; talk with your health care provider about whether to continue having mammograms if you are aged 75 years or older
Cancer of the cervix* Pap test Women aged 21–29 years Every 3 years
Co-testing (Pap
test plus HPV test)
Women aged 30 years and older Every 5 years; it is acceptable to have a Pap test alone every 3 years.
You should stop having cervical cancer screening after age 65 if you do not have a history of moderate or severe dysplasia or cancer and you have had either three negative Pap test results in a row or two negative co-test results in a row, with the most recent test performed within the past 5 years.
Colon and rectal
(choose one)
Colonoscopy Women aged 50 years and older Every 10 years
Fecal occult blood test (FOBT) or fecal immunochemical testing Women aged 50 years and older Yearly
Flexible sigmoidoscopy Women aged 50 years and older Every 5 Years
Double contrast barium enema test Women aged 50 years and older Every 5 years
Computed tomography Women aged 50 years and older Every 5 years
Fecal DNA test Women aged 50 years and older Unknown
HPV indicates human papillomavirus
*Women who have a history of cervical cancer, have human immunodeficiency virus (HIV) infection, are immunocompromised, or who were exposed to diethystilbestrol in utero should not follow these routine guidelines.

What lifestyle changes can help reduce the risk of cancer?

  • Do not smoke.
  • Limit your intake of fat (especially saturated fat and trans fat).
  • Eat foods with high fiber content.
  • Get regular health checkups.
  • Exercise every day for at least 30 minutes.
  • Limit your time in the sun and use sun block when you go outside.
  • Limit your number of sexual partners.
  • Have recommended exams and tests.
  • Limit the amount of alcohol you drink.

Are there self-exams for cancer?

Yes. There are several kinds of self-exams that may alert you to changes in your body that may signal a problem.

  • Vulvar self-exam—Do this exam once a month. This exam is shown in “Disorders of the Vulva: Common Causes of Vulvar Pain, Burning, and Itching.”
  • Skin self-exam—Check your skin regularly to look for any unusual changes. Check any moles regularly to see if the shape, color, or size has changed. Have your health care provider examine your moles at your checkups.

You also should be aware of changes in your breasts and report any changes to your health care provider.


Cervix: The opening of the uterus at the top of the vagina.

Colon: The part of the large intestine that leads into the rectum.

Colonoscopy: An exam of the entire colon using a small, lighted instrument.

Computed Tomography (CT): A type of X-ray procedure that shows internal organs and structures in cross section.

Double Contrast Barium Enema Test: A test during which a special solution and air are injected into the colon and X-ray images are taken to check for abnormalities in the colon.

Fecal Occult Blood Test (FOBT): A test of a stool sample for blood, which could be a sign of cancer of the colon or rectum.

Genes: DNA “blueprints” that code for specific traits, such as hair and eye color.

Human Immunodeficiency Virus (HIV): A virus that attacks certain cells of the body’s immune system and causes acquired immunodeficiency syndrome (AIDS).

Human Papillomavirus (HPV): The common name for a group of related viruses, some of which cause genital warts and cervical cancer.

Mammography: A procedure in which X-rays of the breast are used to detect breast cancer.

Ovaries: Two glands, located on either side of the uterus, that contain the eggs released at ovulation and that produce hormones.

Pap Test: A test in which cells are taken from the cervix and examined under a microscope.

Rectum: The last part of the digestive tract.

Saturated Fat: Fat that is waxy or solid at room temperature and comes mostly from animals.

Sigmoidoscopy: A test in which a slender device is placed into the rectum and lower colon to look for cancer.

Trans Fat: Fat that comes from adding hydrogen to vegetable oils to improve their smell, taste, and shelf life.

Uterus: A muscular organ located in the female pelvis that contains and nourishes the developing fetus during pregnancy.

Vagina: A tube-like structure surrounded by muscles leading from the uterus to the outside of the body.

Vulva: The external female genital area.

If you have further questions, contact your obstetrician–gynecologist.

Designed as an aid to patients, this document sets forth current information and opinions related to women’s health. The information does not dictate an exclusive course of treatment or procedure to be followed and should not be construed as excluding other acceptable methods of practice. Variations, taking into account the needs of the individual patient, resources, and limitations unique to the institution or type of practice, may be appropriate.