Dysplasia; Human papillomas virus; Pap smear
The changes that lead to cervical cancer develop slowly. Screening tests performed during regular gynecologic examinations can detect early changes.
Every year in the U.S. about 50 million women have a Papanicolaou test (the Pap smear). Use of the Pap smear has significantly reduced the death rate from cervical cancer.
Many women who have a Pap smear fail to follow-up for retesting and treatment. Most cases of cervical cancer occur in women who have not had regular Pap tests.
The Procedure. The most accurate test results are obtained 12 - 14 days after menstruation begins. Women should not douche or have intercourse within 48 hours of the test. Douches and spermicidal creams may clean out abnormal cells and interfere with the results of a Pap smear. (In general, douching is not recommended at all.) A Pap smear is usually painless, although some women may have some discomfort.
Reliability and Accuracy. The Pap smear is not a perfectly reliable measure of a woman's risk for cervical cancer. In general, about 10% of Pap smears 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 smear 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 without a significant danger.
New tests and methods have been developed to improve the accuracy of the Pap smear in detecting cancer cells. For example, there are several computerized Pap test systems that are used to rescreen the original smear. These systems are either used to detect abnormal samples that may have been missed by manual review methods or are used in place of a human cytotechnologist. There is not yet enough evidence to know whether or not computerized methods are superior to conventional Pap testing.
Newer, thin-layer liquid based tests (ThinPrep, SurePath) use the original cervical sample, which is rinsed in a special solution to thin the mucus (rather than dried). The fluid is examined for evidence of abnormal cells as well as HPV and other early abnormalities. Some, but not all, studies have found liquid-based Pap tests to be more accurate than the standard Pap smear.
General guidelines for cervical cancer screening recommend:
Initial Screening. Women should begin to undergo Pap tests within 3 years of onset of sexual activity or at age 21 (whichever comes first).
Women with no history of sexual activity should still have Pap smears. They are at low risk for squamous cell carcinoma, but adenocarcinoma (cancer that occurs in cervical glands) can occur, although this is very uncommon.
Women Up to Age 30. Women under age 30 should receive annual screening with the conventional Pap smear. The American Cancer Society (ACS) offers the alternative of screening every 2 years using the newer liquid-based testing. HPV testing is not recommended for this age group because HPV infections in women under age 30 tend to resolve on their own.
Women Age 30 and Over. Women in this age group who have received three consecutive negative (normal) annual Pap tests have two screening options:
Elderly Women. The U.S. Preventive Service Task Force recommend against routine screening in women over age 65 with low or no risk factors. (The ACS recommends stopping at age 70, while the American College of Obstetricians and Gynecologists declines to set an upper age limit.) Such women have had at least three previous normal screenings and have had no abnormal results for at least 10 years. Older women should be screened if they have not been screened before or if there is a possibility that they have not been screened (for example, if the woman is from a country that does not do routine screening). However, some doctors recommend continued screening for elderly women with intact uteruses who are sexually active but not monogamous.
After a Hysterectomy. Women who have had a total hysterectomy (removal of uterus and cervix) for non-cancer reasons may choose to discontinue Pap testing. Women who have had a hysterectomy that preserves the cervix (called a supracervical hysterectomy) should continue with Pap screening.
If Pap smear results are normal for 3 consecutive years, most doctors recommend a Pap test every 2 - 3 years thereafter in most women over 30 years of age. (The American Cancer Society suggests that such women wait until they are 30 before extending the interval to 3 years.)
Both the American Cancer Society and the American College of Obstetricians and Gynecologists recommend that annual screening should continue in women in high-risk categories. High risk categories may include:
A human papilloma virus (HPV) DNA test can identify the high-risk types of HPV that are known to cause cervical cancer. The presence of these types is a strong predictor of high-grade aggressive abnormalities or cancer itself. Testing for HPV does not replace the Pap smear, but when used in combination with the Pap test this screening combination may help to more accurately detect cervical cell abnormalities than either test alone.
The HPV DNA test is recommended as a screening test for:
The cells viewed in a cervical smear sample are classified on a scale representing the spectrum of cell changes from normal to cancerous. The smear is first characterized as either "normal" or "abnormal."
Once abnormal epithelial cells are identified, the doctor must decide whether the patient needs only repeat Pap smears, a test for the human papilloma virus (HPV) virus, or colposcopy (a procedure used to magnify the cervix and permit detection of 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). The two main types of cervical cell cancer are squamous cell and 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.
These classifications are based on the 2001 Bethesda System (TBS), which is formulated to standardize the reporting of Pap test results:
Atypical Squamous Cells. Atypical squamous cells (ASC) are mildly abnormal cells on the surface of the cervix. They may simply represent inflammation. Over 80% of these cells normalize, but unfortunately, between 5 - 17% of these women have a chance for having cervical intraepithelial neoplasia (CIN) II and III dysplasia, which indicatespotentially invasive cells Atypical squamous cells are further categorized as:
Among those with atypical squamous cells, immunosuppressed women and those with high-risk human papilloma virus infections are at higher risk for cervical intraepithelial neoplasia II and III and should always be given colposcopy. Postmenopausal women with normal immune systems have a lower risk than younger women. In general, the actual risk for cervical cancer in women with atypical squamous cells is only 0.1 - 0.2%.
Squamous Intraepithelial Lesions (SILs). Squamous intraepithelial lesions (SILs) are classified as either low-grade or high-grade. 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.
The Pap smear shows only the presence of abnormal cells. It is useful simply as a screening test that identifies women who may have preinvasive 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 precancerous 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:
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. The doctor usually advises sexual abstinence for 1 - 2 weeks.
Follow-Up Procedures. Women with evidence of cervical intraepithelial neoplasia (CIN) or cervical cancer require 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 include 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.
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