|Abnormal Pap stain, Hospital of Monfalcone, Italy|
Abnormal cells on a Pap smear are often associated with the discovery of cervical cancer, but negative results on the test do not necessarily indicate cancer. Transient infection, other causes of inflammation, and problems with the sample are all potential reasons for abnormal results. An abnormal Pap smear result means that additional testing is necessary, usually a second test a few months after the first abnormal results. Doctors may pursue additional tests to confirm the findings and determine if there are any risks of cancer.
The Pap smear is a technique used to evaluate changes in cervical cells. Gynecologists and clinicians use specially designed tools to painlessly scrape or brush endothelial cells from the cervix, which are then evaluated by a pathologist for any deviations from the expected normal in regards to size, shape, and condition. Most labs use the Bethesda system for grading the cells. Approximately 6 percent of Pap smears have abnormal results according to the National Cancer Institute, 10 percent according to the American Pregnancy Association. Though an abnormal Pap smear test is the earliest indicator of cervical cancer, not all abnormal results mean that the test found cancer. An abnormal Pap result simply means that further testing is necessary.
Infection and inflammation
The most common reason for an abnormal Pap smear is human papillomavirus (HPV) infection. Though some strains of HPV have been linked to cancer development, they can also cause genital warts and asymptomatic transient infection is very common. In women whose immune systems do not clear the virus, infection may lead to cervical intraepithelial neoplasia. Follow-up Pap smears can help doctors determine whether the infection is persistent, and an HPV test can confirm the infection and verify the strain. Other infections, including herpes and yeast, can also result in an abnormal Pap test. Another Pap smear a few months later that returns normal results will confirm that it was transient inflammation in the previous result.
The original abnormal results may be reported as “atypical squamous cells” (ASC), usually with undetermined significance, which is the most common abnormal finding. HPV infection may also cause low-grade squamous intraepithelial lesions and require biopsy to determine the risk of cancer.
Dysplasia is alteration of the cervical cells being evaluated and the first step in cancer formation. The degree of dysplasia is reported based on the thickness of the cervical cell layer that is abnormal. High-grade squamous intraepithelial lesions indicate severe dysplasia or carcinoma in situ – precancerous lesions. Changes in glandular cells may also be found, which may or may not indicate adenocarcinoma.
False positive or unsatisfactory sample
Recent sexual activity and some feminine hygiene products may result in unsatisfactory samples for pathological evaluation. Also, like any other test, Pap tests have a risk of false positive results, meaning that a woman is told she has abnormal cells when they are actually normal. The rate is estimated at less than 5 percent. The smears are also manually evaluated and open to examiner error. The various reasons for abnormal results are why annual and follow-up testing is recommended.