Pap Smear Terminology
A classification system for reporting Pap smear results, called Bethesda System 2001, was published in the Journal of the American Medical Association in April 2002. The 2001 Bethesda System terminology was developed by a Consensus Conference of over 50 international professional medical societies under sponsorship of the National Cancer Institute (National Institutes of Health, US Department of Health & Human Services). This version replaces a system originally developed in 1988.
Bethesda System 2001 Terminology:
Important Sections of the Report and the New Terminology
Specimen Adequacy: Each laboratory must report if the cervical sample obtained for the test was adequate and if the quality of the smear was satisfactory for examining under the microscope. Before looking at the results, one should always check to see if the smear has been marked "Satisfactory." If "unsatisfactory," the reasons will be given and the smear will have to be repeated in 2 or 3 months.
Interpretation/Results: This is the section where the important findings from looking at the cells are reported. There are four different sections:
- Negative for intraepithelial lesion or malignancy
- Other: Endometrial cells present in a woman age 40 or more
- Epithelial Cell Abnormalities
- Other Malignancies
Negative for intraepithelial lesion or malignancy:
This is the desired result and where a "normal" result is reported. There are two important subcategories, where abnormal findings not related to the risk of cancer are reported. These are:
- ORGANISMS: This is where evidence of Trichomonas, a fungal (yeast) infection, Herpes, or some other infection is reported.
- OTHER NON-NEOPLASTIC FINDINGS: This is where evidence of injury and response to injury, previously termed "Benign Cellular Changes," is reported.
Other: Endometrial cells present in a woman age 40 or more:
This section is used to alert the physician that endometrial cells (cells from the lining of the uterus) are present when they normally should not be. This is a check on the status of the uterus and endometrium and not the cervix.
Epithelial Cell Abnormality:
This section is where abnormalities that are associated with the risk of developing cancer are reported. The abnormalities range from changes which are only slightly abnormal to definite cancer. There is a spectrum of change. There are two types of epithelial cells in the cervix (squamous and glandular) and changes in each are listed.
Squamous Abnormalities (cells that cover most of the external part of the cervix)
- Atypical Squamous Cells: Unknown Significance (ASC-US) or Cannot exclude HSIL or high-grade changes (ASC-H)
- Low Grade Squamous Intraepithelial Lesion (LSIL)
- High Grade Squamous Intraepithelial Lesion (HSIL); one subcategory: "with features suspicious for malignancy"
- Squamous Cell Carcinoma
The potential for malignancy increases as you move down the list to the last diagnosis of Squamous Cell Carcinoma, which is an invasive cancer.
Note: There are over 50 million Pap smears done in the US each year and approximately 4,000 new cancers are reported. The odds of a positive Pap smear for cancer are quite small.
Glandular Abnormalities (cover the lining of the uterus opening and canal)
- Atypical cells, not otherwise specified
- Atypical cells, favor neoplastic
- Adenocarcinoma in situ
- Adenocarcinoma (can be endometrial (uterus), endocervical (cervix), extrauterine (origin from outside uterus and cervix), or the site of the malignancy cannot be determined based on the Pap smear))
Glandular abnormalities are much less common than squamous abnormalities. The list above is arranged so that the potential for malignancy increases as you move down the list. A diagnosis like adenocarcinoma in situ (a cancer limited to the surface which has not invaded) is one of the rarest diagnoses made on a Pap smear and frequently requires consultation among pathologists.
Malignant tumors other than primary squamous carcinoma and glandular adenocarcinoma are occasionally seen on a Pap smear and they are reported here.
It is important that if you do not understand your Pap smear results, you ask your medical practitioner for clarification. Ninety-nine percent of the abnormal findings reported on a Pap smear are either completely benign or completely reversible and treatable. However, annual Pap smear testing remains important to ensure that any potentially serious problems are detected promptly.
- Communication from Kenneth Sims, MD based on Dr. John Bishops' topic "Pap Smear" in Evaluating Abnormal Test Results developed by the University Pathology Consortium, LLC.