Abnormal Pap Smear Results: What Do They Mean?

One of the most common abnormal findings on a Pap smear—a routine screening test for cervical cancer and any abnormal cell changes on the cervix that might lead to cervical cancer—is known as ASCUS. ASCUS is an acronym for atypical squamous cells of undetermined significance.

ASCUS doesn't mean that you have or will ever get cancer, but it signifies that there have been changes in cells that require further investigation and monitoring.

Other abnormal Pap smear findings that don't necessarily suggest cancer but may require additional testing include squamous intraepithelial lesion (SIL) and atypical glandular cells (ACG).

This article explains what ASCUS and other abnormal Pap test findings mean, including how common they are and how certain abnormalities can progress to cancer. It also explains what happens next if you get an abnormal Pap smear result.

Abnormal Pap Smear Results

If abnormal or unusual cells are discovered during your Pap smear, this is said to be a positive result. Keep in mind that a positive result doesn't necessarily mean you have cervical cancer. 

There are several classifications used to describe abnormal Pap smear results.

Atypical Squamous Cells of Undetermined Significance (ASCUS)

Atypical squamous cells of undetermined significance (ASCUS) is the most common abnormal finding from a Pap smear. It means that some of the cells from a Pap smear did not look entirely normal but did not meet the diagnostic criteria for a lesion (meaning an area of abnormal tissue).

The risk of cancer following an ASCUS result is relatively low because between one-third and two-thirds of these results are not due to the human papillomavirus virus (HPV), the predominant cause of cervical cancer.

ASCUS can also be the result of other sexually transmitted infections (STIs), a vaginal yeast infection, cervical polyps, cysts, or other conditions that cause vaginal irritation or inflammation. Low hormone levels in postmenopausal women can also lead to an ASCUS diagnosis.

Even so, your healthcare provider may want to repeat the Pap smear or perform other diagnostic tests and procedures, such as a cervical biopsy.

Several risk factors can increase your odds of cervical cancer and indicate the need for routine screening, including:

• Having multiple sex partners
• Having given birth to three or more children
• Using birth control pills
• Smoking
• Having HIV
  

Squamous Intraepithelial Lesion (SIL)

A squamous intraepithelial lesion (SIL) is an area of abnormal cells that forms on the surface of the cervix. SIL can be considered precancer but is best described as dysplasia (meaning the abnormal growth of cells).

SIL may be classified as either a low-grade squamous intraepithelial lesion (LSIL) or a high-grade squamous intraepithelial lesion (HSIL). LSIL is very common and typically goes away on its own without treatment. HSIL may lead to cancer if left untreated.

Atypical Glandular Cells (AGC)

A finding of atypical glandular cells (AGC) occurs when mucus-secreting cells from the inner part of the cervix or lining of the uterus exhibit changes that are significant but lack the distinctive features of cancer.

AGC is used when the changes are likely too pronounced to be inflammatory (such as with cervicitis) or reactive (such as due to injury, IUDs, or radiation) but fall short of what would be expected with a malignancy (cancer).

AGC may be a sign of cancer or precancer, but may also be due to certain reactive or inflammatory conditions. More testing is needed.

Squamous Cell Cancer or Adenocarcinoma Cells

Both squamous cell carcinoma (SCC) and adenocarcinoma are cancers. Of the two, SCC is the most common cause of cervical cancer, accounting for roughly 80% of cases, while adenocarcinoma accounts for 15% to 20%.

While it is less common than SCC, adenocarcinoma of the cervix tends to be more aggressive and have poorer outcomes.

Normal Pap Smear But Positive HPV Test

If your Pap smear is read as normal, your healthcare provider will also consider the results of your HPV test or recommend an HPV test on the same sample if it was not previously done.

If both your Pap smear and HPV test are normal—and if you do not have a history of abnormal Pap smears/HPV tests—you likely won't need any further testing or treatment until your next recommended screening test. This is usually five years for HPV testing or co-testing.

If your Pap smear is normal but your HPV test is positive, your healthcare provider will talk to you about possible recommendations. According to the American Society for Colposcopy and Cervical Pathology (ASCCP), for women aged 30 years or older who are HPV-positive with a normal Pap smear, repeat testing can be done in one year.

If any repeat HPV test is positive or a Pap smear shows a significant abnormality, colposcopy (a procedure that closely examines the cervix, vagina, and vulva) is recommended.

Follow-Up After an Abnormal Pap Smear

The recommended follow-up after an abnormal Pap smear depends on the findings, any treatment you receive, your age, your history of Pap smears and HPV testing in the past, and more. Follow-up usually includes more frequent screening, such as HPV/Pap testing and colposcopy.

It's important to note that for people who have significantly abnormal Pap smears (such as those that are HSIL or precancerous), HPV testing or HPV testing plus a Pap smear will be required every three years for a full 25 years. The reason for this is that the risk of cervical cancer with these findings persists for at least 25 years.

Reflex Testing

Reflex testing is when you have a Pap smear and the same cells are also tested for HPV, or if you have an HPV test and a Pap test is performed on the same cells.

HPV Typing

HPV typing is an HPV test that looks for the two main HPV strains that cause cervical cancer: types 16 and 18. These are If you test positive for HPV, this typing may be done.

Repeat Testing

For people under 25 years of age, a repeat Pap may be done in six months to a year, depending on the results. For those over 25, a repeat Pap may be done or both a repeat Pap and HPV testing may be recommended. The specific time period when this is done depends on your age, medical history, previous Pap results, and abnormal results.

Colposcopy, Biopsy, and Endocervical Sampling

Those who are at high risk for high-grade abnormal cells may be referred for a colposcopy, biopsy, and endocervical sampling. A colposcopy uses a special magnifying device to examine the cervix and any abnormal areas.

A biopsy involves removing a sample of tissue from the cervix for further examination in a lab. Endocervical sampling involves scraping and collecting cells from the endocervical canal (the passageway from the uterus to the vagina) to be examined in a lab.

Endometrial Sampling

If glandular cells show up on the Pap, this can be concerning and an endometrial sampling may be done. A small piece of tissue from the uterine lining (endometrium) is biopsied so it can be sent to a lab for further testing.

Cervical Cancer Healthcare Provider Discussion Guide

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Prevention

If you've had an abnormal Pap smear or HPV test, careful follow-up and lifestyle measures may reduce your risk of developing cervical cancer. For example, while smoking does not cause cervical cancer directly, it appears to increase the chance that people who develop high-risk HPV infections will go on to develop cancer.

In addition, HPV vaccination (Gardasil 9) is recommended for all people between the ages of 9 and 26, whether or not they have been sexually active. If you were not vaccinated within this window of time, you may still get the vaccine up until age 45. Your provider can help you evaluate if it makes sense in your case.

A Swedish study found that among women vaccinated under the age of 17, the incidence of cervical cancer was 88% lower than those who were not vaccinated. For those vaccinated later (between the ages of 17 and 30), the incidence was 53% lower.

Summary

A Pap smear is a procedure that screens for cervical cancer. A negative result means that no abnormal cells were found. A positive result means that there are changes in cells that may or may not be a sign of cancer but are concerning enough to warrant further investigation.

Depending on your Pap smear result, follow-up testing may be necessary. This depends on the type of changes seen, the result of your HPV test, and your medical history.

A Word From Verywell

It's important to remember that an abnormal pap doesn't necessarily mean cervical cancer. This screening test helps healthcare professionals fully evaluate the cervix so that if there is an abnormality, it can be caught early and treated before it progresses to a more significant finding.

— CORDELIA NWANKWO, MD, MEDICAL EXPERT BOARD