Abnormal Pap Smear Results: What Do They Mean?

A Pap smear, also known as a Pap test, screens for cervical cancer and any abnormal cell changes on the cervix that might lead to cervical cancer. One of the most common abnormal findings is something called atypical squamous cells of undetermined significance, or ASCUS. 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.

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 offers insights as to what happens next if you get an abnormal Pap smear result.

What Is a Pap Smear?

A Pap smear involves collecting cells from the vagina and cervix—the lower, narrow end of the uterus, at the top of the vagina. It's usually done in conjunction with a pelvic exam. Pap smears look for abnormal cell changes that may lead to cancer and they also test for precancers. These precancers are often caused by human papillomavirus (HPV).

Human papillomavirus is a very common sexually transmitted infection (STI) that can lead to cervical cancer in some women. While there are many strains of HPV, only certain strains are linked to cervical cancer.

An HPV test is a test for these high-risk, cancer-causing strains of HPV that can be done at the same time as a Pap test. It may also be performed on a Pap sample after it has been sent to a lab.

Normal Pap Smear Results

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 screening test is recommended. This is usually five years for HPV testing or co-testing.

Normal Pap But Positive HPV Test

If your Pap smear is normal but your HPV test is positive, your healthcare provider will talk to you about possible recommendations. Most commonly, this combination of results means that an HPV infection is present but not causing any abnormalities in the cervical cells at the time. Most HPV infections clear without causing abnormalities or cancer.

Sometimes, these results could be a false negative (a test result that incorrectly indicates a condition is not present) if the Pap smear sample did not pick up an area of abnormal cells.

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.

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 classification used to describe an 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).

ASCUS is not cancer nor precancer and may or may not ever lead to cancer. Even so, the changes warrant further investigation and monitoring.

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

With ASCUS, your healthcare provider may either repeat the Pap smear or perform other diagnostic tests and procedures, such as a biopsy.

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) is 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 or 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.

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), after the initial period of increased screening, 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 those same cells are also tested for HPV, or if you have an HPV test and a Pap test may be performed on those same cells.

HPV Typing

HPV typing is an HPV test that looks for the two main HPV strains that cause cervical cancer. These are types 16 and 18. 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, your medical history, your previous Pap results, and your 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. Enndocervical 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. When these cells show up on a Pap, endometrial sampling may be done. This is when a small piece of tissue from the uterine lining, or 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 physician 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

Detecting cervical cancer early with a Pap smear gives you a greater chance of a cure. The National Institutes of Health currently advises that Pap screening start at age 21.

If you have an abnormal result, you should get a Pap smear every three years if you're between the ages of 21 and 29. People 30 and older have several options: a Pap test every three years, an HPV test every five years, or a Pap and HPV test every five years.

A yearly gynecologic exam should be conducted irrespective of how often a Pap smear is performed.