Cervical cancer screening
What is cervical cancer screening?
Cervical cancer screening is used to find changes in the cells of the cervix that could lead to cancer. Screening includes cervical cytology (also called the Pap test or Pap smear), testing for human papillomavirus (HPV), or both. Most women should have cervical cancer screening on a regular basis.
How does cervical cancer occur?
The cervix is the opening to the uterus and is located at the top of the vagina. It is covered by a thin layer of tissue made up of two types of cells: 1) “skin-like” cells called squamous cells and 2) glandular cells that produce the mucus in the cervix.
Cancer occurs when cervical cells become abnormal and, over time, grow out of control. The cancer cells invade deeper into the cervical tissue. In advanced cases, cancer cells can spread to other organs of the body.
What causes cervical cancer?
Most cases of cervical cancer are caused by infection with HPV. HPV is a virus. It enters cervical cells and can cause them to change. Some types of HPV have been linked to cervical cancer as well as to cancer of the vulva, vagina, penis, anus, mouth, and throat. Types of HPV that may cause cancer are known as “high-risk types.”
These and other types of HPV can be passed from person to person during sexual activity. HPV is very common—most people who are sexually active will get an HPV infection in their lifetime. HPV infection often causes no symptoms. Most people do not even know they are infected.
Does HPV always lead to cervical cancer?
Only a small number of women with high-risk types of HPV will get cervical cancer. Because of the body’s natural ability to fight infection, most HPV infections go away on their own. These short-term infections typically cause only mild, or “low-grade,” changes in cervical cells. The cells go back to normal as the HPV infection clears.
In a small number of women, HPV does not go away. If HPV infection lasts for a long time, it is described as a “persistent” infection. Persistent HPV infection with high-risk types can cause more severe, or “high-grade,” changes in cervical cells. High-grade changes that persist for 1 or 2 years are more likely to become cancer if they are not treated.
Factors such as cigarette smoking, a weak immune system, and infection with human immunodeficiency virus (HIV) are thought to increase the chance that HPV infection will persist, but persistent infections also occur in women without these factors.
Why is cervical cancer screening important?
It usually takes 3 to 7 years for high-grade changes in cervical cells to become cancer. Cervical cancer screening may detect these changes before they become cancer. Women with low-grade changes can be tested more frequently to see if their cells go back to normal. Women with high-grade changes can get treatment to have the cells removed.
Cervical cancer screening saves lives. Over the past 30 years in the United States, the number of cases of cervical cancer and deaths has decreased by one half. This is mainly the result of women getting regular cervical cancer screening.
How is cervical cancer screening done?
Cervical cancer screening includes the Pap test, an HPV test, or both. Both tests use cells taken from the cervix. The screening process is simple and fast. You lie on an exam table and a speculum is used to open the vagina. The speculum gives a clear view of the cervix and upper vagina.
Cells are removed from the cervix with a brush or other sampling instrument. The cells usually are put into a special liquid and sent to a laboratory for testing:
- For a Pap test, the sample is examined to see if abnormal cells are present.
- For an HPV test, the sample is tested for the presence of the most common high-risk HPV types. Usually, the sample taken for the Pap test also can be used for the HPV test. Sometimes, two cell samples are taken. It depends on the type of Pap test that is used.
How often should I have cervical cancer screening and which tests should I have?
Cervical cancer screening is an important part of women’s health care. You should start having screening at age 21, regardless of when you first start having sex. How often you should have cervical cancer screening and which tests you should have depend on your age and health history:
- Women who are 21 to 29 should have a Pap test alone every 3 years. HPV testing alone can be considered for women who are 25 to 29, but Pap tests are preferred.
- Women who are 30 to 65 have three options for testing. They can have a Pap test and an HPV test (co-testing) every 5 years. They can have a Pap test alone every 3 years. Or they can have HPV testing alone every 5 years.
When should I stop having cervical cancer screening?
Women should stop having cervical cancer screening after age 65 if
- they do not have a history of moderate or severe abnormal cervical cells or cervical cancer, and
- they have had either three negative Pap test results in a row, two negative HPV tests in a row, or two negative co-test results in a row within the past 10 years. The most recent test should have been performed within the past 3 or 5 years, depending on the type of test.
If I have had a hysterectomy, do I still need cervical cancer screening?
Women who have had a hysterectomy may still need to have screening. The decision is based on whether the cervix was removed, why the hysterectomy was needed, and whether there is a history of severe cervical cell changes or cervical cancer.
Even if the cervix is removed at the time of hysterectomy, cervical cells can still be present at the top of the vagina. If you have a history of cervical cancer or high-grade cervical cell changes, you should continue to have screening for 20 years after the time of your surgery.
How else can I protect myself from cervical cancer?
The HPV vaccine is an important way to help protect against the HPV infections that most commonly cause cancer. But the HPV vaccine does not protect against all types of HPV that can cause cancer. So women who have been vaccinated against HPV still need to follow the cervical cancer screening recommendations for their age group.
Are there women who may need more frequent screening?
Women who have a history of cervical cancer, are infected with HIV, have a weakened immune system, or who were exposed to diethylstilbestrol (DES) before birth may require more frequent screening and should not follow these routine guidelines.
Why is cervical cancer screening not recommended before age 21?
Cervical cancer is extremely rare in this age group. Fewer than 1 in 1,000 cases of cervical cancer occur in young women 15 to 19. Most women become infected with HPV shortly after they begin having vaginal intercourse. These infections almost always go away on their own within 1 to 2 years without causing any changes in the cervical cells. If changes do occur, the cells almost always go back to normal. Research shows that cervical cancer screening in this age group does not reduce the rate of cervical cancer and can lead to unnecessary treatment.
Why is yearly screening not recommended?
Research over the past decades shows that there is no overall advantage to having yearly Pap tests over having Pap tests every 3 years. Yearly Pap tests do find a slightly higher number of cases of cancer than tests performed every 3 years. But women who have yearly screening undergo many more follow-up tests and treatments for what turns out not to be cancer than women who have testing every 3 years.
Some follow-up tests, such as colposcopy and cervical biopsy, and treatment options, such as a loop electrosurgical excision procedure (LEEP), are invasive procedures that can be uncomfortable. Having an unnecessary test or treatment is inconvenient and can cause anxiety. Limiting the number of these unnecessary procedures is one of the goals of current cervical cancer screening guidelines.
Why is cervical cancer screening recommended even if I am not having sex?
In rare cases, HPV can be spread by genital contact without sexual intercourse. This may include genital contact with someone of the same sex. In addition, although HPV is the main cause of cervical cancer, it’s not the only cause. Other factors, such as smoking and HIV infection, can affect your risk for getting HPV and developing cervical cancer.
Why is co-testing (Pap test plus HPV test) not recommended for women who are 21 to 29?
HPV infection is common in this age group. These infections usually go away on their own within a few years and do not cause any lasting changes in cervical cells. Use of co-testing in women younger than 30 would mostly detect short-term HPV infections that would not lead to cancer. This testing would result in more frequent and unnecessary follow-up testing.
Are these guidelines likely to change again?
Yes. Experts continue to develop new and better ways to screen for cervical cancer and manage abnormal results. Experts also are learning more about HPV infection and how it affects women of different ages. The goal is to develop a testing strategy that finds the most cases of cervical cancer or precancerous changes with the least number of unnecessary follow-up tests and treatments.
Do I still need to see my ob-gyn every year if yearly cervical cancer screening is no longer recommended?
Yes. It is still important to see your obstetrician–gynecologist (ob-gyn) regularly for a routine care visit. These visits are an opportunity for you to learn about how to prepare for pregnancy, discuss your birth control options, or address menopause issues.
In addition, your ob-gyn can help you identify whether you are at risk of certain medical conditions, such as diabetes mellitus or heart disease. They also can give certain vaccinations—including the HPV vaccine—if you are due for them. And your visit may include a pelvic exam or a clinical breast exam.
What does it mean if I have an abnormal cervical cancer screening test result?
Many women have abnormal cervical cancer screening results. An abnormal result does not mean that you have cancer. Remember that cervical cell changes often go back to normal on their own. If they do not, it often takes several years for even high-grade changes to become cancer.
If you have an abnormal screening test result, additional testing is needed to find out whether high-grade changes or cancer actually is present. If results of follow-up tests indicate high-grade changes, you may need treatment to remove the abnormal cells. See Abnormal Cervical Cancer Screening Test Results for more information.
How accurate are cervical cancer screening test results?
As with any lab test, cervical cancer screening results are not always accurate. Sometimes, the results show abnormal cells when the cells are normal. This is called a false-positive result. Cervical cancer screening also may not detect abnormal cells when they are present. This is called a false-negative result.
Many factors can cause false results:
- The sample may contain too few cells.
- There may not be enough abnormal cells to study.
- An infection or blood may hide abnormal cells.
- Douching or vaginal medications may wash away or dilute abnormal cells.
To help prevent false-negative or false-positive results, you should avoid douching, sexual intercourse, and using vaginal medications or hygiene products for 2 days before your test. And while you can have cervical cancer screening when you have your menstrual period, it is best to schedule screening at another time. Your period can affect the accuracy of the results.