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- 65.
- The HPV (human papillomavirus) test, which may be used along with a Pap test or after a woman has had an abnormal Pap test result. The HPV test can identify the high-risk types of HPV that are known to cause cervical cancer. This test is 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 on its own within 2 years.
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. To help get the most accurate results, doctors recommend scheduling a Pap test for the 10 - 20 days after menstruation begins. Those are the best days for obtaining the most accurate results. The Pap test should not be performed during menstruation.
In the 24 - 48 hours before the test:
- Do not have sexual intercourse
- Do not use vaginal spermicides, lubricants, or tampons
- Do not douche (in general, douching is not recommended at all)
The Procedure. A Pap test is usually painless, although some women may have some discomfort.
- The test is done in a doctor's 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 doctor inserts a plastic or metal device (called a speculum) into her vagina to widen it.
- Using a spatula, brush, or both, the doctor gently scrapes the surface of the cervix, and sometimes the upper vagina, to gather living cells. The doctor will also obtain cells from inside the cervical canal. The scraping is completely painless.
- The cells are preserved, stained for microscopic viewing, and then analyzed under a microscope by a specialist known as a cytopathologist.
Reliability and Accuracy. The Pap test is not a perfectly reliable measure of a woman's risk for cervical cancer. In general, about 10% of Pap tests have abnormal results, but only about 0.1% of the women who have these results actually have cancer. In most cases, abnormal cells are low grade and not likely to progress to cancer or are due to benign conditions, including natural cell changes after menopause.
No test is 100% accurate, and it is possible for the Pap test to miss the presence of cancer. However, if abnormal cells are missed on one test, they are likely to be spotted during the next one. It is also possible for a test to indicate abnormal cells when the cells are really normal. If a test indicates possible abnormal cells, your doctor will order another Pap test or additional other tests to confirm the results.
HPV DNA Test
For a HPV test, the doctor 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 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 may also be used to provide more information after an abnormal Pap test in women ages 21 years and older.
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 - 29. Women ages 21 - 29 who are at average risk for cervical cancer should be screened once every 3 years with a Pap test. They do not need a HPV test unless they have had an abnormal Pap test result.
Women Ages 30 - 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.
How Pap Test Results Are Reported
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.
Once abnormal epithelial cells are identified, the doctor must decide whether the patient needs a repeat Pap test, an HPV test, or more invasive testing with colposcopy and biopsy. (Colposcopy is a procedure used to magnify the cervix and to help find lesions for biopsy). To help the doctor make the decision, the abnormal cells are divided into categories, depending on the degree of abnormality, and whether they are squamous or glandular (adenocarcinoma).
Squamous cell carcinoma represents the large majority of all cervical cancers. The remaining cases are either a combination of squamous and glandular, or rarer types.
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) or atypical glandular cells.
Atypical Squamous Cells. Atypical squamous cells (ASC) 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 be caused by inflammation. Atypical squamous cells 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 very often not pre-cancerous. Women with ASC-US need to have a repeat Pap test in 6 - 12 months and the doctor may also recommend a HPV test and possibly colposcopy.
- ASC-H. This category refers to atypical squamous cells 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). All are referred for colposcopy.
Squamous Intraepithelial Lesions (SILs). Squamous intraepithelial lesions (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 identify the presence of SILs but not their grade. All patients with SILs 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 cancerous changes than atypical squamous cells or low-grade squamous intraepithelial lesions. Patients with atypical glandular cells need colposcopy and endocervical testing. 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 definitive diagnosis, the next step is usually colposcopy, during which the cervix is visualized under low power magnification. The surgeon takes samples of suspicious cells for biopsies. A biopsy will determine the stage of the pre-cancerous growth or whether invasive cancer is present.
The Procedure. Colposcopy can be performed in a doctor's office without anesthesia in 10 - 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.
- A biopsy (a sampling of the tissue) is taken of suspicious areas, of the endocervical canal (the inner part of the cervix and uterus), and any abnormal-looking areas. This may cause cramping or pinching.
Click the icon to see an image of colposcopy-directed biopsy.
After the colposcopy, the woman may have a brownish discharge from an iron solution called Monsel's solution, which the doctor applies to prevent bleeding. Doctors usually advise sexual abstinence for 1 - 2 weeks.
The pre-cancerous changes from biopsy results of colposcopy are called cervical intraepithelial neoplasia. They are graded according to severity: 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 high-grade squamous intraepithelial lesion.
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 deeper tissues. However, if not surgically removed, there is a high chance that CIN III or CIS can progress to invasive cancer.
Follow-Up Procedures. Women with evidence of cervical intraepithelial neoplasia (CIN) or cervical cancer need treatment. Women with biopsies that show low-grade abnormal cells, but whose cervix is otherwise normal, are generally given follow-up colposcopies.
If a biopsy detects invasive cancer, the patient will need additional tests to find out how far the cancer has spread. Tests to stage cancer may include a computed tomography (CT) scan (to check for the spread of the disease to lymph nodes and areas around the pelvic region), chest x-ray, ultrasound, magnetic resonance imaging (MRI), positron emission tomography (PET) scan, and other imaging tests.