Cervical Cancer: Prevention and Early Detection

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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 (sometimes called the Pap smear) and the HPV (human papilloma virus) test are used for this. If a pre-cancer is found, it can be treated, stopping cervical cancer before it really starts. Since no HPV vaccine provides complete protection against all of the HPV types that can cause cancer of the cervix, it cannot prevent all cases of cervical cancer. This is why it is very important that women continue to have Pap tests, even after they’ve been vaccinated. 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 (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 health care 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 later in this section under the heading “How biopsy results are reported”). 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 true. 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 (sometimes with a HPV 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. Women who have been diagnosed with cervical cancer should have follow-up testing as recommended by their healthcare team.

The Papanicolaou (Pap) test

The Pap test is the main screening test for cervical cancer and pre-cancerous changes.

Although the Pap test has been more successful than any other screening test in preventing a cancer, it’s 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 looked at in the best laboratories), it’s not a good idea to have this test less often than American Cancer Society guidelines recommend.

A Pap test is not the same as a pelvic exam

Many people confuse pelvic exams with Pap tests. The pelvic exam is part of a woman’s routine health care. During a pelvic exam, the doctor looks at and feels the reproductive organs, including the uterus and the ovaries and may do tests for sexually transmitted disease. 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 during a 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. Ask your doctor if you had a Pap test with your pelvic exam.

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 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. The 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 (see illustration in “What is cervical cancer?” section). A small brush or a cotton-tipped swab is then inserted into the opening of the cervix to take a sample from the endocervix (see illustration in “What is cervical cancer?” section). The cell samples are then prepared so that they can be examined under a microscope in the laboratory. This this is done in 2 main ways.

Conventional cytology: One way is to smear the sample directly onto a glass microscope slide, which is then sent to the laboratory. For about 50 years, all cervical cytology samples were handled this way. 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 with direct smears 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 done again. Conventional cytology is not often used in the US at this time.

Liquid-based cytology: The other way is to put the sample of cells from the cervix into a special preservative liquid (instead of putting them directly on a slide) and then send it to the lab. Technicians then 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 seem to 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 more expensive than a usual Pap test.

Another way to improve the Pap test is by using computerized instruments that can spot abnormal cells in Pap tests. A machine that can read Pap tests has been approved by the FDA to read Pap tests first (instead of them being examined by a technologist). It’s also approved by the FDA for rechecking Pap test results that were read as normal by technologists. Any smear identified as abnormal by the machine would then be reviewed by a doctor or a technologist.

Computerized instruments can find abnormal cells that technologists sometimes miss. Most of the abnormal cells found this way are in rather early stages, such as atypical squamous cells (ASCs), but sometimes high-grade abnormalities missed by human testing can be found. Scientists do not know yet whether the instrument can find enough high-grade abnormalities missed by human testing to have a real impact on preventing invasive cervical cancers. Automated testing also increases the cost of 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.

Making your Pap tests more accurate

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

  • Try not to schedule an appointment for a time during your menstrual period. The best time is at least 5 days after your menstrual period stops.
  • Don't use tampons, birth-control foams or jellies, other vaginal creams, moisturizers, or lubricants, or vaginal medicines for 2 to 3 days before the test.
  • Don't douche for 2 to 3 days before the test.
  • Don’t have sexual intercourse for 2 days before the test.

Is there a Pap test you can do at home?

Doctors have been trying to find ways to get more women involved in cervical cancer screening. Some have proposed methods that would allow women to take cervical cell samples at home. For this test, a woman would collect cervical cells herself by inserting a small plastic applicator into the vagina and moving it around on the cervix. This would be put in a special container to preserve the cells. Women in poorer countries have used this method to check for sexually transmitted diseases, and it has also been useful to check for HPV infections. So far, however, no “home-based” Pap test has been approved for use in the United States. Currently, the American Cancer Society does not recommend any at-home Pap test.

How Pap test results are reported

The most widely used system for describing Pap test results is the Bethesda System (TBS). There are 3 main categories, some of which have sub-categories:

  • 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 infection with yeast, herpes, or Trichomonas vaginalis (a microscopic parasite), for example. Specimens from some women may also show “reactive cellular changes”, which is the way cervical cells respond to infection or other irritation.

Epithelial cell abnormalities

This 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:

Atypical squamous cells (ASCs): This category includes atypical squamous cells of uncertain significance (ASC-US) and atypical squamous cells where high-grade squamous intraepithelial lesion (SIL) can’t be excluded (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 this is caused by infection, 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 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 subdivided 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. They 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 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 called adenocarcinomas. In some cases, the pathologist examining the cells can tell 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, the term used is atypical glandular cells (AGCs). The patient should have more testing if her cervical cytology result shows atypical glandular cells.

Other malignant neoplasms

This category is for forms of cancer that only rarely affect the cervix, such as malignant melanoma, sarcomas, and lymphoma.

Other descriptions of Pap test results have also been used in the past.

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 (high-risk or carcinogenic types) that are most likely to cause cervical cancer 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 it sometimes can even be done on the same sample.

The HPV DNA test can be used in 2 situations:

  • The HPV gene test can be used in combination with the Pap test to screen for cervical cancer in women 30 and older (see American Cancer Society screening guidelines). 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 documents, What Women Should Know About Cervix Cancer and the Human Papilloma Virus and Thinking About Testing for HPV?
  • 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 the next section).

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 to see if you test positive 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 get repeat co-testing in one year.

Last Medical Review: 05/02/2013
Last Revised: 02/04/2014