Cervical Cancer

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Causes, Risk Factors, and Prevention TOPICS

Can cervical cancer be prevented?

Since the most common form of cervical cancer starts with pre-cancerous changes, there are 2 ways to stop this disease from developing. The first way is to find and treat pre-cancers before they become true cancers, and the second is to prevent the pre-cancers.

Finding cervical pre-cancers

A well-proven way to prevent cervix cancer is to have testing (screening) to find pre-cancers before they can turn into invasive cancer. The Pap test (or Pap smear) and the human papilloma virus (HPV) test are used for this. If a pre-cancer is found it can be treated, stopping cervical cancer before it really starts (treatment is discussed in the section, "How are cervical cancers and pre-cancers treated?"). Most invasive cervical cancers are found in women who have not had regular Pap tests.

The American Cancer Society recommends the following guidelines for early detection:

  • All women should begin cervical cancer testing (screening) at age 21. Women aged 21 to 29, should have a Pap test every 3 years. HPV testing should not be used for screening in this age group (although it may be used as a part of follow-up for an abnormal Pap test).
  • Beginning at age 30, the preferred way to screen is with a Pap test combined with an HPV test every 5 years. This is called co-testing and should continue until age 65.
  • Another reasonable option for women 30 to 65 is to get tested every 3 years with just the Pap test.
  • Women who are at high risk of cervical cancer because of a suppressed immune system (for example from HIV infection, organ transplant, or long term steroid use) or because they were exposed to DES in utero may need to be screened more often. They should follow the recommendations of their healthcare team.
  • Women over 65 years of age who have had regular screening in the previous 10 years should stop cervical cancer screening as long as they haven’t had any serious pre-cancers (like CIN2 or CIN3) found in the last 20 years (CIN stands for cervical intraepithelial neoplasia and is discussed in the section about cervical biopsies, in “How are cervical cancers and pre-cancers diagnosed”). Women with a history of CIN2 or CIN3 should continue to have testing for at least 20 years after the abnormality was found.
  • Women who have had a total hysterectomy (removal of the uterus and cervix) should stop screening (such as Pap tests and HPV tests), unless the hysterectomy was done as a treatment for cervical pre-cancer (or cancer). Women who have had a hysterectomy without removal of the cervix (called a supra-cervical hysterectomy) should continue cervical cancer screening according to the guidelines above.
  • Women of any age should NOT be screened every year by any screening method.
  • Women who have been vaccinated against HPV should still follow these guidelines

Some women believe that they can stop cervical cancer screening once they have stopped having children. This is not correct. They should continue to follow American Cancer Society guidelines.

Although annual (every year) screening should not be done, women who have abnormal screening results may need to have a follow-up Pap test done in 6 months or a year.

The American Cancer Society guidelines for early detection of cervical cancer do not apply to women who have been diagnosed with cervical cancer or those with HIV infection. These women should have follow-up testing as recommended by their healthcare team.

Although the Pap test has been more successful than any other screening test in preventing a cancer, it is not perfect. One of the limitations of the Pap test is that it needs to be examined by humans, so an accurate analysis of the hundreds of thousands of cells in each sample is not always possible. Engineers, scientists, and doctors are working together to improve this test. Because some abnormalities may be missed (even when samples are examined in the best laboratories), it is not a good idea to have this test less often than American Cancer Society guidelines recommend.

Making your Pap tests more accurate

You can do several things to make your Pap test as accurate as possible:

  • Try not to schedule the appointment for a time during your menstrual period. The best time is at least 5 days after your menstrual period stops.
  • Do not douche for 48 hours before the test.
  • Do not have sexual intercourse for 48 hours before the test.
  • Do not douche or use tampons, birth control foams, jellies, or other vaginal creams, moisturizers or lubricants, or vaginal medicines for 48 hours before the test.

Pelvic exam versus Pap test

Many people confuse pelvic exams with Pap tests. The pelvic exam is a routine part of a woman's health care. During a pelvic exam, the doctor looks at the vulva, vagina, and cervix and feels the reproductive organs, including the cervix, uterus and the ovaries and may do tests for sexually transmitted diseases.

Pap tests are often done during pelvic exams, but you can have a pelvic exam without having a Pap test. A pelvic exam without a Pap test will not help find abnormal cells of the cervix or cervical cancer at an early stage.

The Pap test is often done at the start of the pelvic exam, after the speculum is placed. To do a Pap test, the doctor removes cells from the cervix by gently scraping or brushing it with a special instrument. Pelvic exams may help find other types of cancers and reproductive problems, but a Pap test is needed to find early cervical cancer or pre-cancers.

How the Pap test is done

Cytology is the branch of science that deals with the structure and function of cells. It also refers to tests to diagnose cancer and pre-cancer by looking at cells under the microscope. The Pap test (or Pap smear) is a procedure used to collect cells from the cervix for cervical cytology testing.

The health care professional first places a speculum inside the vagina. A speculum is a metal or plastic instrument that keeps the vagina open so that the cervix can be seen clearly. Next, using a small spatula, a sample of cells and mucus is lightly scraped from the exocervix (the surface of the cervix that is closest to the vagina). A small brush or a cotton-tipped swab is then inserted into the cervical opening to take a sample from the endocervix (the inside part of the cervix that is closest to the body of the uterus). The cell samples are then prepared so that they can be examined under a microscope in the laboratory. This is done in 2 main ways:

Conventional cytology

One method is to smear the sample directly onto a glass microscope slide, which is then sent to the laboratory. All cervical cytology samples were handled in this way for at least 50 years. This method works quite well and is relatively inexpensive, but it does have some drawbacks. One problem with this method is that the cells smeared onto the slide are sometimes piled up on each other, making it hard to see the cells at the bottom of the pile. Also, white blood cells (pus), increased mucus, yeast cells, or bacteria from infection or inflammation can hide the cervical cells. Another problem is that if the slides are not treated (with a preservative) right away, the cells can dry out. This can make it difficult to tell if there is something wrong with the cells. If the cervical cells cannot be seen well (because of any of these problems), the test is less accurate, and it might need to be repeated.

Liquid-based cytology

Another method is to put the sample of cells from the cervix into a special preservative liquid (instead of putting them on a slide directly). The bottle containing the cells and the liquid is sent to the lab. Technicians then use special lab instruments to spread some of the cells in the liquid onto glass slides to look at under the microscope. This method is called liquid-based cytology, or a liquid-based Pap test. The liquid helps remove some of the mucus, bacteria, yeast, and pus cells in a sample. It also allows the cervical cells to be spread more evenly on the slide and keeps them from drying out and becoming distorted. Cells kept in the liquid can also be tested for HPV. Using liquid-based testing may reduce the chance that the Pap test will need to be repeated, but it does not find more pre-cancers than a regular Pap test. The liquid-based test is also more likely to find cell changes that are not pre-cancerous but that will need to be checked out further − leading to unnecessary tests. This method is also more expensive than the usual Pap test.

Another way to improve the Pap test is by using computerized instruments to spot the abnormal cells on the slides. The FDA has approved an instrument to read Pap tests first (instead of them being examined by a technologist) and to recheck Pap test results that were read as normal by technologists. Any result identified as abnormal by this instrument would then be reviewed by a doctor or a technologist.

Although the hope was that using computerized instruments would find abnormal cells that technologists might sometimes miss, studies so far have not found a real advantage for the automated testing. Automated testing also increases the cost of the cervical cytology testing.

For now, the best way to detect cervical cancer early is to make certain that all women are tested according to American Cancer Society guidelines. Unfortunately, many of the women most at risk for cervical cancer are not being tested often enough or at all.

How Pap test results are reported

The most widely used system for describing Pap test results is The Bethesda System (TBS). This system has been revised twice since it was developed in 1988: first in 1991 and, most recently, in 2001. The information that follows is based on the 2001 version. The 3 general categories are:

  • Negative for intraepithelial lesion or malignancy
  • Epithelial cell abnormalities
  • Other malignant neoplasms

Negative for intraepithelial lesion or malignancy

This first category means that no signs of cancer, pre-cancerous changes, or other significant abnormalities were found. Some specimens in this category appear entirely normal. Others may have findings that are unrelated to cervical cancer, such as signs of infections with yeast, herpes, or Trichomonas vaginalis (a microscopic parasite), for example. Specimens from some cases may also show reactive cellular changes, which is the way cervical cells respond to infection or other irritation.

Epithelial cell abnormalities

The second category, epithelial cell abnormalities, means that the cells lining the cervix or vagina show changes that might be cancer or a pre-cancerous condition. This category is divided into several groups for squamous cells and glandular cells.

The epithelial cell abnormalities for squamous cells are called:

Atypical squamous cells (ASC): This category includes atypical squamous cells of uncertain significance (ASC-US) and atypical squamous cells, cannot exclude high-grade squamous intraepithelial lesion (ASC-H).

ASC-US is a term used when there are cells that look abnormal, but it is not possible to tell (by looking at the cells under a microscope) if the cause is infection or irritation, or if it is a pre-cancer. Most of the time, cells labeled ASC-US are not pre-cancer, but more testing is needed to be sure.

If the results of a Pap test are labeled ASC-H, it means that a high-grade SIL is suspected.

Pap test results of either type of ASC mean that more testing is needed. This is discussed in the section, “Work-up of abnormal Pap test results.”

Squamous intraepithelial lesions (SILs): These abnormalities are divided into low-grade SIL (LSIL) and high-grade SIL (HSIL). In LSIL, the cells are mildly abnormal, while in HSIL, the cells are severely abnormal. HSILs are less likely than LSILs to go away without treatment. HSILs are also more likely to eventually develop into cancer if they are not treated. Treatment can cure most SILs and prevent true cancer from developing.

Further tests are needed if SIL is seen on a Pap test. This is discussed in the section, “Work-up of abnormal Pap test results.”

Squamous cell carcinoma: This result means that the woman is likely to have an invasive squamous cell cancer. Further testing will be done to be sure of the diagnosis before treatment can be planned.

The Bethesda System also describes epithelial cell abnormalities for glandular cells.

Adenocarcinoma: Cancers of the glandular cells are reported as adenocarcinomas. In some cases, the pathologist examining the cells can suggest whether the adenocarcinoma started in the endocervix, in the uterus (endometrium), or elsewhere in the body.

Atypical glandular cells: When the glandular cells do not look normal, but have features that do not permit a clear decision as to whether they are cancerous, they are called atypical glandular cells. The patient should have more testing if her cervical cytology result shows atypical glandular cells.

The HPV DNA test

As mentioned earlier, the most important risk factor for developing cervical cancer is infection with HPV. Doctors can now test for the types of HPV that are most likely to cause cervical cancer (high-risk types) by looking for pieces of their DNA in cervical cells. The test is done similarly to the Pap test in terms of how the sample is collected, and in some cases can even be done on the same sample. The HPV DNA test is used in 2 different situations.

  • The HPV DNA test can be used with the Pap test to screen for cervical cancer in women 30 years of age and older (see American Cancer Society screening guidelines above). It does NOT replace the Pap test. Women in their 20s who are sexually active are much more likely (than older women) to have an HPV infection that will go away on its own. For these younger women, results of this test are not as significant and may be more confusing. For this reason, the HPV DNA test is not recommended as a screening test in women under 30. For more information, see the American Cancer Society document, What Every Woman Should Know About Cervical Cancer and the Human Papilloma Virus.
  • The HPV DNA test can also be used in women who have slightly abnormal Pap test results (ASC-US) to find out if they might need more testing or treatment (see next section).

Follow-up tests

If you have an abnormal result on a Pap test, other tests will need to be done to find out if you actually have a cancer or a pre-cancer and to decide what treatment (if any) is needed. These tests are discussed in the section, "How is cervical cancer diagnosed?" and the section “Work-up of abnormal Pap test results.” Treatment of abnormal Pap results is discussed in the section, "Treating pre-cancers and other abnormal Pap test results."

If your Pap test result is normal, but you test positive for HPV, there are 2 main options.

  • Repeat co-testing (with a Pap test and an HPV test) in one year
  • Testing for HPV types 16 or 18 (this can often be done on the sample in the lab). If you are, colposcopy would be recommended (colposcopy is discussed in the section, “How is cervical cancer diagnosed?”). If you test negative, you should have repeat co-testing in one year.

Things to do to prevent pre-cancers

Avoid being exposed to HPV

Since HPV is the main cause of cervical cancer and pre-cancer, avoiding exposure to HPV could help you prevent this disease. HPV is passed from one person to another during skin-to-skin contact with an infected area of the body. Although HPV can be spread during sex − including vaginal intercourse, anal intercourse, and oral sex − sex doesn't have to occur for the infection to spread. All that is needed is skin-to-skin contact with an area of the body infected with HPV. This means that the virus can be spread through genital-to-genital contact (without intercourse). It is even possible for a genital infection to spread through hand-to-genital contact.

Also, HPV infection seems to be able to be spread from one part of the body to another. This means that an infection may start in the cervix and then spread to the vagina and vulva.

It can be very hard not to be exposed to HPV. It may be possible to prevent genital HPV infection by not allowing others to have contact with your anal or genital area, but even then there may be other ways to become infected that aren’t yet clear.

In women, HPV infections occur mainly in younger women and are less common in women older than 30. The reason for this is not clear. Certain types of sexual behavior increase a woman's risk of getting genital HPV infection, such as having sex at an early age and having many sexual partners. Women who have had many sexual partners are more likely to get infected with HPV, but a woman who has had only one sexual partner can still get infected. This is more likely if she has a partner who has had many sex partners or if her partner is an uncircumcised male.

Waiting to have sex until you are older can help you avoid HPV. It also helps to limit your number of sexual partners and to avoid having sex with someone who has had many other sexual partners. Although the virus most often spreads between a man and a woman, HPV infection and cervical cancer are seen in women who have only had sex with other women.

HPV does not always cause warts or any other symptoms; even someone infected with HPV for years might have no symptoms. Someone can have the virus and pass it on without knowing it.

HPV and men

For men, the main factors influencing the risk of genital HPV infection are circumcision and the number of sexual partners.

Men who are circumcised (have had the foreskin of the penis removed) have a lower chance of becoming and staying infected with HPV. Men who have not been circumcised are more likely to be infected with HPV and pass it on to their partners. The reasons for this are unclear. It may be that after circumcision, the skin on the glans (of the penis) goes through changes that make it more resistant to HPV infection. Another theory is that the surface of the foreskin (which is removed by circumcision) is more easily infected by HPV. Still, circumcision does not completely protect against HPV infection − men who are circumcised can still get HPV and pass it on to their partners.

The risk of being infected with HPV is also strongly linked to having many sexual partners (over a man's lifetime).

Condoms and HPV

Condoms (" rubbers") provide some protection against HPV. Men who use condoms are less likely to be infected with HPV and to pass it on to their female partners. One study found that when condoms are used correctly they can lower the HPV infection rate in women by about 70% if they are used every time they have sex. One reason condoms cannot protect completely is that they don't cover every possible HPV-infected area of the body, such as skin of the genital or anal area. Still, condoms provide some protection against HPV, and they also protect against HIV and some other sexually transmitted diseases. Condoms (when used by the male partner) also seem to help the HPV infection and cervical pre-cancers go away faster.

Don't smoke

Not smoking is another important way to reduce the risk of cervical pre-cancer and cancer.

Get vaccinated

Vaccines have been developed that can protect women from HPV infections. So far, a vaccine that protects against HPV types 6, 11, 16 and 18 (Gardasil®) and one that protects against types 16 and 18 (Cervarix®) have been studied. Cervarix was approved by the FDA in 2009 for use in the United States, while Gardasil has been approved for use in this country since 2006. Gardasil is also approved to prevent anal, vaginal, and vulvar cancers and pre-cancers and to prevent anal and genital warts. Both vaccines require a series of 3 injections over a 6-month period. The side effects are usually mild. The most common one is short-term redness, swelling, and soreness at the injection site. Rarely, a young woman will faint shortly after the vaccine injection. Cervarix is approved for use in girls and young women ages 10 to 25 years, while Gardasil is approved for use in both sexes aged 9 to 26 years old.

In clinical trials, both vaccines prevented cervical cancers and pre-cancers caused by HPV types 16 and 18. Gardasil also prevented anal, vaginal, and vulvar cancers caused by those HPV types, as well as genital warts caused by HPV types 6 and 11. Cervarix also provides some protection against infection and pre-cancers of the cervix by high-risk HPV types other than HPV 16 and 18. It has also been shown to prevent anal infection with HPV types 16 and 18.

Both Gardasil and Cervarix only work to prevent HPV infection − they will not treat an infection that is already there. That is why, to be most effective, the HPV vaccine should be given before a person becomes exposed to HPV (such as through sexual activity).

In 2009, the Federal Advisory Committee on Immunization Practices (ACIP) published updated recommendations for HPV vaccination in girls and young women. It recommended that females aged 11 to 12 routinely be vaccinated with the full series of 3 shots. Females as young as age 9 may also receive the HPV vaccine at the discretion of their doctors. ACIP also recommended women ages 13 to 26 who have not yet been vaccinated get "catch-up" vaccinations. Either vaccine may be used to prevent cervical cancers and pre-cancers. However, the ACIP recommends using Gardasil to prevent genital warts as well as cervical cancers and pre-cancers.

These vaccines should be given with caution to anyone with severe allergies. Women with a severe allergy to latex should not take the Cervarix vaccine, and those with a severe allergy to yeast should not receive Gardasil.

The American Cancer Society guidelines recommend that the HPV vaccine be routinely given to females aged 11 to 12 and as early as age 9 years at the discretion of doctors. The Society also recommends that catch-up vaccinations should be given to females up to age 18.

The independent panel making the Society recommendations found that there was not enough proof that catch-up vaccinations for all women aged 19 to 26 years would be beneficial. As a result, the American Cancer Society recommends that women aged 19 to 26 talk with their health care provider before making a decision about getting vaccinated. They should discuss the risks of previous HPV exposure and potential benefit from vaccination before deciding to get the vaccine. At this time, the American Cancer Society’s guidelines do not address the use of the vaccine in older women and males.

Both types of cervical cancer vaccines are expensive − costing about $375 for the full series of injections (not including the doctor's fee or the cost of giving the injections). Either vaccine should be covered by most medical insurance plans (if given according to ACIP guidelines). It should also be covered by government programs that pay for vaccinations in children under 18. Because vaccination costs so much, you may want to check your coverage with your insurance company before getting the vaccine.

It is important to realize that neither vaccine completely protects against all cancer-causing types of HPV, so routine cervical cancer screening is still necessary.

For more information on the vaccine and HPV, please see our document, Human Papilloma Virus (HPV), Cancer, and HPV Vaccines: Frequently Asked Questions


Last Medical Review: 04/11/2013
Last Revised: 08/15/2014