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What Are Atypical Squamous Cells of Undetermined Significance (ASCUS)?

ASCUS cardA Pap smear looks for abnormal cells, and there are various terms to describe these abnormalities. Most detected abnormalities are due to either reactive change or a treatable, premalignant condition known as dysplasia or squamous intraepithelial lesion. Rarely, however, abnormal cells are encountered in screening which are not easily classified as either reactive or premalignant, and their significance is therefore uncertain. These cells are not of typical appearance (and are, therefore, atypical) and are called Atypical Squamous Cells of Undetermined Significance (ASCUS).

Your provider may need to perform follow-up studies for ASCUS findings.  HPV testing can be helpful to determine the type of follow-up tests needed. Your doctor will determine the appropriate treatment.

More information on ASCUS and the special testing used following the diagnosis is available at info/pdq/prevention.

What Happens to my Pap Smear?

Many people believe that the Pap smear is an automated test, similar to a blood test. In fact, evaluation of a Pap test is a very labor-intensive, manual process. Although automated machines have been developed to aid in the review of normal-appearing Pap smears, routine screening of every Pap test must also be performed by a professional cytotechnologist.

After your doctor collects your Pap smear, it is sent to a laboratory where it is processed and reviewed by a cytotechnologist.  Cytotechnologists are highly trained professionals who have a bachelor’s degree followed by one year of special training in cytology.  The cytotechnologist looks at the individual cells on your Pap test using a microscope. If any abnormalities are detected, the Pap test is also reviewed by a pathologist, a physician specially trained to evaluate tissues and cells under a microscope. After review, a report of the results is sent to your doctor.

What are the Limitations of the Pap Smear?

The Pap smear is an imperfect test. Despite its many successes, the test occasionally fails to detect disease. This can happen in two ways.

First – and most common – the disease may not be present in the smeared collection, a situation known as sampling variability. Second, it can occur as a result of not detecting abnormal cells on a slide. Such “false-negative” smears occur in every laboratory. It is estimated that a skilled cytotechnologist will misinterpret one out of every 100 to 400 smears. This is the equivalent of one “miss” for every one to two weeks screening. The limitations are best overcome by regular interval testing.

Why Do I Need Regular Interval Testing?

A regularly scheduled Pap test and possibly HPV test, is believed to be the best way to counter the drawbacks of the Pap test (see “Limitations” above). Since cervical cancer, in most instances, takes several years to develop, regular testing provides more than one opportunity to catch the disease in an early, treatable state. Most women with abnormal Pap smears have subsequent therapy which completely removes the areas of abnormality. The most important step in early treatment, however, is early detection.  This is best provided by Pap screening at regular intervals.