The changes that lead to cervical cancer develop slowly. Screening tests performed during regular gynecologic examinations can detect early changes. The two tests used for cervical cancer screening are:
- The Pap test, which can detect pre-cancerous cell changes and cervical cancer. This test is used for all women ages 21 to 65.
- The HPV (human papillomavirus) test, which may be used along with a Pap test or after a woman has an abnormal Pap test result. It may also be used as a primary test. The HPV test can identify the high-risk types of HPV that are known to cause cervical cancer. This test is generally not used for women younger than age 30 because HPV is very common in this age group. In younger women, the virus usually goes away within 2 years as a result of the body successfully fighting it off.
The Papanicolaou test, better known as the Pap test or Pap smear, can help detect cervical cancer when it is in its earliest stages. It can also detect pre-cancerous changes in cells.
Use of the Pap test has significantly reduced the death rate from cervical cancer. Most cases of cervical cancer occur in women who have not had regular Pap tests.
Preparing for a Pap Test
Doctors recommend scheduling a Pap test 10 to 20 days after menstruation begins to get the most accurate results. The Pap test should not be performed during menstruation.
In the 24 to 48 hours before the test, DO NOT:
- Have sexual intercourse
- Use vaginal spermicides, lubricants, or tampons
Pap Test Procedure
A Pap test is usually painless, although some women may have mild discomfort:
- The test is done in a medical office. The woman removes her clothes from the waist down and puts on a medical gown. She lies on her back on the examination table, bends her knees, and puts her feet in supports (called stirrups) at the end of the table.
- The health care provider inserts a plastic or metal device (called a speculum) into her vagina to widen it.
- Using a spatula, brush, or both, the provider gently scrapes the surface of the cervix, and sometimes the upper vagina, to gather living cells. The provider will also obtain cells from inside the cervical canal. The scraping is completely painless.
- The cells are preserved either on a glass slide or, now more commonly, in liquid. They are processed at the lab and stained for microscopic viewing, and then analyzed under a microscope by a specialist known as a cytopathologist. One of the advantages of the liquid-based test is that the same specimen can be used for additional tests (HPV, other STIs, and vaginal infections).
A Pap test is a simple, relatively inexpensive procedure that can easily detect cancerous or pre-cancerous conditions.
Reliability and Accuracy
The Pap test is not a perfectly reliable measure of a woman's risk for cervical cancer. Sometimes it misses the presence of cancer or pre-cancer cells, which is called a false-negative result. However, if abnormal cells are missed on one test, they are likely to be spotted during the next one, hopefully while they are still in the pre-cancerous state, which makes treatment significantly easier and safer.
It is also possible for a test to indicate abnormal cells when the cells are really normal, a so-called false positive result. If a test indicates possible abnormal cells, your provider will order another Pap test or other tests to confirm the results.
HPV DNA Test
For an HPV DNA test, the provider collects a sample of the cervical cells the same way (and usually at the same time) as the Pap test. This test looks for the types of human papillomavirus (particularly HPV 16 and HPV 18) that cause cervical cancer by analyzing the DNA of the cervical cells.
The HPV test can be used along with the Pap test to screen for cervical cancer in women ages 30 years and older. It is also approved as a single test for women ages 25 and older to see if they need further diagnostic testing with a Pap test or colposcopy. The test can provide information on a women's risk of developing cervical cancer in the future.
Current Cervical Cancer Screening Recommendations
General guidelines for cervical cancer screening recommend:
- Initial Screening. Women should begin to have Pap tests at age 21 regardless of whether or not they have been sexually active. Women under age 21 should not be screened.
- Women Ages 21 to 29. Women ages 21 to 29 who are at average risk for cervical cancer should be screened once every 3 years with a Pap test. They do not need an HPV DNA test unless they have had an abnormal Pap test result. In 2014, the FDA approved an HPV test as primary screening for women ages 25 and older. Cancer experts are currently reviewing guidelines on how the HPV test should be used.
- Women Ages 30 to 65. Women in this age bracket can have either a Pap test every 3 years or a Pap test and HPV test every 5 years.
- Women Ages 65 and Older. Women age 65 and older no longer need Pap tests as long as they have had regular Pap tests with normal results. Women who have been diagnosed with pre-cancer should continue to receive regular screenings.
- After a Hysterectomy. Women who have had a hysterectomy that preserves the cervix (called a supracervical hysterectomy) should continue to have Pap screening according to the guidelines listed above. Women who have had their cervix removed at the time of hysterectomy no longer need Pap tests, unless the hysterectomy was done for cervical cancer or pre-cancer in which cases screening should be continued.
Pap Test Results
The cells viewed in a cervical smear sample are classified on a scale representing the spectrum of cell changes from normal to cancerous. The Pap test is first characterized as either normal or abnormal.
The Bethesda System (TBS) is used to report Pap test results. It classifies abnormal results as:
- Atypical squamous cells (ASC with subtypes of ASC-US and ASC-H)
- Squamous intraepithelial lesions (SILs)
- Atypical glandular cells
Atypical Squamous Cells (ASC)
ASCs are mildly abnormal cells on the surface of the cervix. It is difficult to know if they are pre-cancerous. They may be normal cells with changes simply caused by inflammation. ASCs are further categorized as ASC-US or ASC-H:
- ASC-US. Atypical squamous cells of undetermined significance (ASC-US) are the lowest risk abnormal cells and are most often not pre-cancerous. Women with ASC-US need to have a repeat Pap test in 6 to 12 months and the doctor may also recommend an HPV test and possibly colposcopy.
- ASC-H. This category refers to ASC that may indicate high-grade squamous intraepithelial lesions (HGSIL). Such women have a higher risk of having CIN II and III (moderate or severe dysplasia) and hence are at risk for development of cervical cancer. They are referred for colposcopy.
Squamous Intraepithelial Lesions (SILs)
SILs are classified as either low-grade (LGSIL) or high-grade (HGSIL). High-grade SILs are more serious than low-grade SILs, and need to be treated because they can develop into invasive cancer. Pap tests can suggest the presence of SILs but not their grade. Women with SILs discovered through a Pap test should undergo colposcopy. A colposcopy can determine whether SILs are high-grade or low-grade and whether treatment is required.
Atypical Glandular Cells and Adenocarcinoma
Atypical glandular cells pose a higher risk for the presence of cancerous changes than atypical squamous cells. Women with atypical glandular cells need a pelvic ultrasound, colposcopy, and endocervical and endometrial testing, to rule out the presence of cancer. Adenocarcinoma refers to glandular cells that are cancerous.
Colposcopy and Biopsy
The Pap test shows only the presence of abnormal cells. It is useful simply as a screening test that identifies women who may have pre-invasive or early cancerous changes. For a diagnosis, the next step is usually colposcopy, during which the cervix is visualized under low power magnification. The doctor takes small samples of the cervix for biopsies. A biopsy will determine the grade of the pre-cancerous growth or whether invasive cancer is present.
Colposcopy can be performed in a medical office without anesthesia in 10 to 15 minutes. It causes about as much discomfort as mild menstrual cramps:
- First, using a speculum to keep the vagina open, the doctor aims a light at the cervix.
- The doctor then looks through the eyepiece of a special microscope, known as a colposcope, to view the cervix. Application of dilute acetic acid (vinegar) helps bring out the changes caused by SILs.
- A small sample (biopsy) of the cervical tissue is pinched off using forceps.
- After the biopsy, an endocervical scraping (curettage) may be performed to test the tissues of the cervix above the area that can be seen. The doctor uses a spoon-shaped instrument called a curette to scrape tissue from the lining of the endocervical canal, which runs between the cervix and the uterus.
Conization, or cone biopsy, is a more invasive way of doing a biopsy. It is a surgical procedure that uses a scalpel (cold knife biopsy), laser beam, or a wire loop heated by electrical current (LEEP procedure) to remove a larger piece of the cervix. Conization may be performed as a diagnostic procedure, or as a treatment for pre-cancers or early-stage cancers.
The pre-cancerous changes from biopsy results of colposcopy are called cervical intraepithelial neoplasia. They are graded according to severity as CIN I, CIN II, and CIN III:
- CIN I is classified as mild dysplasia. It is equivalent to a low-grade squamous intraepithelial lesion (LGSIL) identified by a Pap test. CIN I may progress if untreated but often goes away without treatment.
- CIN II is classified as moderate dysplasia. It is equivalent to a high-grade squamous intraepithelial lesion (HGSIL) found in a Pap test.
- CIN III is classified as severe dysplasia. It is the most aggressive form of dysplasia. It is also equivalent to a HGSIL.
CIN III is considered the same as carcinoma in situ (CIS) or Stage 0 cervical cancer. In both CIN III and CIS the pre-cancerous cells still rest on the surface of the cervix and have not yet invaded through the basement membrane into the deeper tissues. However, if not surgically removed, there is a high chance that CIN III or CIS can progress to invasive cancer.
Women with evidence of cervical intraepithelial neoplasia (CIN) II and III or cervical cancer need treatment. Women with biopsies that show low-grade abnormal cells or CIN I, but whose cervix is otherwise normal, are generally given follow-up Pap tests or colposcopies.
If a biopsy detects invasive cancer, the woman will need additional tests to find out how far the cancer has spread. Tests to stage cancer may include imaging tests such as:
- Computed tomography (CT) scan
- Chest x-ray
- Magnetic resonance imaging (MRI)
- Positron emission tomography (PET) scan
Other special pelvic exam procedures may also be recommended.
Cervical Cancer Staging
After making a diagnosis, a doctor will classify the stage of the cancer according to the size of the primary tumor, and how far cancer has spread into the lining of the cervix, throughout the cervix, or beyond. Doctors use staging to determine treatment and prognosis.
The basic cervical cancer stages are:
- Stage 0. Cancer is confined only to cells on the lining (epithelium) of the cervix. It is also called carcinoma in situ and is equivalent to CIN III pre-invasive cancer.
- Stage I. Is invasive cancer, but the tumor is confined to the cervix.
- Stage II. Cancer has spread beyond the cervix and uterus, but it has not spread to the pelvic side wall or lower part of the vagina.
- Stage III. Cancer has spread to the lower part of the vagina or sides of the pelvis. It may become large enough to block the ureters of the kidney, which can cause the kidney to stop functioning.
- Stage IV. Is advanced (metastasized) cancer. The cancer has spread to other organs or parts of the body located near the cervix (bladder, rectum) or farther away (liver, lungs).
- Stages I to IV are further subdivided into A and B stages.