Reproductive health

Pap tests: screening for cervical cancer

What is the cervix?

Located in the lower part of a woman's abdomen between the bladder and the rectum, the uterus is a pear-shaped organ. The cervix is the lower, narrower part of the uterus. It forms a canal leading through the vagina and out of the body. The part of the cervix closest to the body of the uterus is called the endocervix (endo = inside). The part next to the vagina is called the ectocervix (ecto = outside). Most cervical cancers begin where the endocervix and ectocervix meet. (See illustration below.)

Pap tests and screening for cancer of the cervix

Pap tests (also called Pap smears) are vital in the early detection of cervical cancer. In fact, in populations around the world where women do not have routine Pap tests, cervical deaths are higher: cervical cancer is the leading cause of death among women in developing countries. This is because these cases are usually diagnosed at an invasive late stage, rather than as precancers or early cancers. Put another way, if all women had pelvic exams and Pap tests regularly, most precancerous conditions would be detected and treated before cancer develops. In addition, Pap tests can also be used to detect vaginal or uterine infections. When such infections are found, they can be treated promptly, thus avoiding further discomfort or more serious complications.

How is the Pap test done?

Simple and painless, the Pap test is used to detect abnormal cells in and around the cervix. Taking only a few minutes, this test is done in a doctor's office or in a health clinic. You'll be asked to lie down on the examination table and to place your feet in stirrups, allowing your knees to fall to the side. A sheet will cover your legs and stomach. Using a speculum to open your vagina will allow your doctor or health care provider to see the upper part of your vagina and cervix and to conduct the Pap test. A wooden spatula and a small brush are used to collect a sample of cells from the cervix and from the upper vagina. This sample is smeared on a glass slide and sent to a medical laboratory to analysis. A cytotechnologist analyzes the sample, checking it for abnormal changes in the cells.

This method of collecting and analyzing cervical cells works quite well and is rather inexpensive. It does, however, have limitations. For instance, cells smeared onto the slide are sometimes piled up on each other, such that cells at the bottom of the pile can't be clearly seen. What's more, infections of the vagina or cervix can cause inflammatory cells, increased mucus, yeast cells, or bacteria, all of which may hide the cervical cells. Cells smeared onto a glass slide can dry out and become distorted as a result. Cells not treated with alcohol to preserve them immediately after they are spread on the slide can become difficult to examine.¹

Some of the mucus, bacteria, yeast, and pus cells can be removed from the cell sample in a newer method called liquid-based cytology (also known as ThinPrep or AutoCyte). In this method, the cell sample is placed in a special preservative solution, rather than being placed directly on the slide. The preservative solution prevents the cells from drying out and becoming distorted, and it also allows cells to be placed more evenly on the slide. Recent studies suggest that liquid-based cytology can slightly improve detection of cancers and greatly improve detection of precancers such as squamous intraepithelial lesion (SIL), a condition that precedes cancer (see below). Although more expensive than a regular Pap smear, liquid-based testing can reduce the number of tests that need to be repeated.²

How reliable is the Pap test?

Pap tests are more reliable than any other screening test in the prevention of cervical cancer. Yet, it isn't perfect. This is because cell samples are examined by humans: accurate analysis of hundreds of thousands of cells in each sample may not always be possible. Because Pap tests aren't always 100% accurate, it's important to discuss the results with your doctor or health care provider. Furthermore, because some abnormalities may be missed, it's not a good idea to avoid Pap tests or to have them less often than recommended by the American Cancer Society (see below).

How can I increase the accuracy of my Pap tests?

There are a number of things you can do to ensure your Pap tests is as accurate as possible:

• Try to avoid scheduling your Pap test during your menstrual period. The best time to have a Pap test is between 10 and 20 days after the first day of your last period.
• Avoid douching, vaginal creams, suppositories, spermicidal foams, vaginal deodorant sprays or powders, or vaginal medications for 48 hours before your Pap test.
• Do not have sexual intercourse for 48 hours before the test.

How are Pap test results reported?

The way of describing Pap results is changing. The newest and most widely used system for describing Pap test results is called The Bethesda System (TBS). Developed in 1988, the Bethesda System describes changes in cervical cells as either low-grade or high-grade squamous intraepithelial lesion (SIL), a condition that precedes cancer. More specifically, TBS classifies results as:

• negative for intraepithelial lesion or malignancy
• epithelial cell abnormalities
• other malignant neoplasms

Negative for intraepithelial lesion or malignancy

No signs of cancer or precancerous changes or other significant changes were found. Some cell samples in this category appear entirely normal while others, although unrelated to cervical cancer, may show evidence of infections of the reproductive system—infections such as yeast, herpes or Trichonomas. Some cells may show reactive cellular changes, a response to infection or other irritation.³

Epithelial cell abnormalities

Epithelial cell abnormalities indicates that cells lining the cervix show changes that may be consistent with cancer or with precancer. This category is further divided into sub-categories for squamous and glandular cells.⁴

Epithelial cell abnormalities for squamous cells are called atypical squamous cells (ASC), low-grade and high-grade squamous intraepithelial lesion (SIL), and squamous cell carcinoma.

Atypical squamous cells

Used when it's not possible to tell whether abnormal cells (as seen under a microscope) are the result of an infection, irritation or precancer, atypical squamous cells require that the Pap test be repeated after several months. Other tests, such as a colposcopy and/or biopsy may be recommended, depending on your history and the results of past Pap tests. Some doctors may recommend a test for human papilloma virus (HPV; the leading cause of cervical cancer) in this situation. If this test shows no HPV, only routine follow up is needed. However, if HPV is found, colposcopy is recommended. (See Diagnostic Tests for more information.)⁵

Squamous intraepithelial lesion

Low-grade SIL refers to early changes in the size, shape, and number of cells that form the surface of the cervix. While some low-grade lesions may go away on their own, others may grow larger or become more abnormal, forming a high-grade lesion. Precancerous low-grade lesions can also be called mild dysplasia or cervical intraepithelial neoplasia 1 (CIN 1). Although these types of early changes in the cervix most commonly occur in women between 25 and 35 years of age, they can appear in other age groups as well.⁶

High-grade SIL refers to the presence of a large number of precancerous cells. As in low-grade SIL, these precancerous changes involve only cells on the surface of the cervix. It will likely take many months—and perhaps years—for these cells to become cancerous and invade deeper layers of the cervix. High-grade lesions can also be called moderate or severe dysplasia, CIN 2 or 3, or carcinoma in situ. While these conditions generally affect women between the ages of 30 and 40, they can occur at other ages as well.⁷

A Pap test cannot determine whether a woman has low-grade or high-grade SIL; it simply indicates that the results fit into one of these abnormal categories. High-grade squamous intraepithelial lesions are less likely than low-grade squamous intraepithelial lesions to go away on their own. These are also more likely to eventually develop into cancer if left untreated. Treatment can cure all squamous intraepithelial lesions and prevent true cancer from developing. Regardless of whether these squamous intraepithelial lesions are classified as low grade or as high grade, all patients should have colposcopy. (See Diagnostic Tests for more information.)⁸

Squamous cell carcinoma

A result of squamous cell carcinoma indicates that a woman likely has an invasive squamous cell cancer. Before a doctor recommends treatment such as radiation therapy, chemotherapy, or radical therapy, this diagnosis must be confirmed by further testing.⁹

Also describing epithelial cell abnormalities for glandular cells, the Bethesda System can also indicate the presence of adenocarcinomas, cancers of the glandular cells. When glandular cells have features that make it unclear whether they are cancerous, they are classified as atypical glandular cells.

Other malignant neoplasms

Unlike squamous cell carcinoma and adenocarcinoma, cancers such as malignant melanoma, sarcomas, and lymphoma—called malignant neoplasms—rarely affect the cervix.

Many doctors believe the Bethesda System provides more useful information than an older system which uses numbers from class 1 to class 5 to classify results. In class 1, cells in the sample are normal while class 5 refers to invasive cancer. Be sure to ask your doctor or health professional about the system used for your Pap test.¹⁰

If the results of your Pap test are normal, no further treatment is needed. If an infection (such as chlamydia, for example) is found, treatment is prescribed. If the cells look abnormal or atypical, more tests may be necessary.

When and how often should I have a Pap test?

There are differing opinions surrounding the appropriate frequency of Pap tests. The American Cancer Society recommends the following guidelines for early detection:

• All women should begin cervical cancer testing (screening) about 3 years after they begin having vaginal intercourse, but no later than when they are 21 years old. Testing should be done every year with the regular Pap test or every 2 years using the newer liquid-based Pap test.
• Beginning at age 30, women who have had 3 normal Pap test results in a row may get tested every 2 to 3 years with either the regular or liquid-based Pap test. Women who have certain risk factors (see Cervical Cancer for information on risk factors) such as diethylstilbestrol (DES) exposure before birth, HIV infection, or a weakened immune system due to organ transplant, chemotherapy, or chronic steroid use should continue to be tested yearly.
• Another reasonable option for women over 30 is to get tested every 3 years (but not more frequently) with either the regular Pap test or the liquid-based Pap test, plus the HPV DNA test (see Diagnostic Tests for more information on this test).
• Women 70 years of age or older who have had 3 or more normal Pap tests in a row and no abnormal Pap test results in the last 10 years may choose to stop having cervical cancer testing. Women with a history of cervical cancer, DES exposure before birth, HIV infection or a weakened immune system should continue to have testing as long as they are in good health.
• Women who have had a total hysterectomy (removal of the uterus and cervix) may also choose to stop having cervical cancer testing, unless the surgery was done as a treatment for cervical cancer or precancer. Women who have had a hysterectomy without removal of the cervix should continue to follow the guidelines above.

Also be sure to read...

Cervical cancer
How can I avoid or prevent cervical cancer?
Diagnostic tests for women with abnormal cervical cytology results
Treating cervical cancer
Pap test
Chlamydia
Human papilloma virus (HPV)

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1. Can Cervical Cancer Be Prevented? American Cancer Society. (2004)
2. Can Cervical Cancer Be Prevented? American Cancer Society. (2004)
3. Can Cervical Cancer Be Prevented? American Cancer Society. (2004)
4. Can Cervical Cancer Be Prevented? American Cancer Society. (2004)
5. Can Cervical Cancer Be Prevented? American Cancer Society. (2004)
6. Precancerous Conditions and Cancer of the Cervix. National Cancer Institute.
7. Precancerous Conditions and Cancer of the Cervix. National Cancer Institute.
8. Can Cervical Cancer Be Prevented? American Cancer Society. (2004)
9. Can Cervical Cancer Be Prevented? American Cancer Society. (2004)
10. Early Detection. National Cancer Institute.