Atypical Squamous Cells

Receiving an abnormal Pap test result can be unsettling, especially if the lab report includes unfamiliar medical terms, such as “atypical squamous cells.” However, this finding is very common and, in most cases, it does not mean cervical cancer is present. Instead, it indicates that some of the cells collected during the Pap test look slightly different than expected and may require further evaluation. Most atypical cervical cell changes are linked to a temporary human papillomavirus (HPV) infection or another benign condition and either resolve on their own or can be monitored and treated before cancer develops.

At Moffitt Cancer Center, the specialists in our gynecologic clinic provide expert evaluations for patients with abnormal Pap test results. Using advanced diagnostic testing and individualized follow-up recommendations, we help our patients understand exactly what their results mean and determine whether additional testing or treatment is needed.

What are squamous cells?

Squamous cells are thin, flat cells that form the outer lining of the cervix, which is the lower portion of the uterus that opens into the vagina. Because these cells are located on the surface of the cervix, they are easily collected during a routine Pap test. 

Does a finding of atypical squamous cells mean I have cancer?

No. A Pap test is a screening test, and the result is not a cancer diagnosis. The purpose of the test is to identify cellular changes that may benefit from closer examination or additional testing. When a pathology report describes squamous cells as atypical, it simply means the cells appear slightly different from typical cervical cells when viewed under a microscope. The changes may be very subtle and often do not indicate precancer or cancer. 

Many abnormal Pap test results are eventually found to be related to a temporary HPV infection or another noncancerous condition. For the overwhelming majority of patients, a finding of atypical squamous cells does not indicate cervical cancer.

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Decoding the lab report

Pap test reports often include medical abbreviations or acronyms that describe the type of cellular changes identified. Although these terms may seem intimidating to some patients, they are simply labels that help healthcare providers determine whether additional testing or monitoring is needed. The two classifications most often associated with atypical squamous cells are ASC-US and ASC-H. 

ASC-US 

ASC-US stands for “atypical squamous cells of undetermined significance.” This is the most common abnormal Pap test result. It means the squamous cells look mildly abnormal, but the changes are too subtle to determine whether they are related to HPV, inflammation or another noncancerous condition. Because the findings are uncertain, an HPV test or repeat Pap test is often recommended to help guide the next steps.

ASC-H

ASC-H stands for “atypical squamous cells, cannot exclude high-grade squamous intraepithelial lesion.” This result indicates that the cells appear more abnormal than those classified as ASC-US, and although the findings are not definitive, a higher-grade precancerous change cannot be ruled out. Although ASC-H does not mean cancer is present, it does warrant timely follow-up because additional testing will be needed to determine whether precancerous changes are present.

Our biggest way to prevent [cervical] cancer moving forward is for women to show up, get vaccinated, and get screening.

Robert Wenham, MD, MS, FACOG, FACS

Department Chair, Gynecologic Oncology

If my Pap test result is abnormal, what will happen next?

An abnormal Pap test usually marks the beginning of a closer evaluation rather than immediate treatment. A healthcare provider will review the Pap test findings along with factors such as the patient’s age, HPV test results and previous cervical screening history to determine the most appropriate next step.

Often, the original cervical cell sample can be tested for high-risk types of human papillomavirus. Although HPV infection is common and usually clears on its own, certain high-risk strains—such as HPV 16 and HPV 18—are associated with an increased risk of cervical cancer. A positive HPV test does not mean cancer is present, but it may indicate that additional evaluation or more frequent cervical screening is appropriate. 

Depending on the patient’s individual situation, the healthcare team may recommend active surveillance (watchful waiting) with a repeat Pap test after a specified interval or additional diagnostic testing, such as:

• Colposcopy – Using a special magnifying instrument (colposcope), the physician will closely examine the cervix for abnormalities. This in-office procedure does not involve surgery.
• Cervical biopsy – If suspicious tissue is identified during a colposcopy, the physician may remove a small sample for microscopic examination by a pathologist, who can determine whether precancerous or cancerous cells are present.
• Endocervical sampling – The physician will collect a small sample of cells from the cervical canal, which cannot always be fully visualized during a colposcopy. This test can help detect abnormal cells located higher within the cervix. 

If my HPV test was negative, what could have caused the atypical squamous cells?

A negative HPV test is reassuring because it suggests that high-risk HPV is unlikely to be responsible for the cellular changes in the cervix. Several other noncancerous conditions can cause squamous cells to appear atypical during a Pap test, including:

• Menopause – Natural hormonal changes associated with menopause may make cervical cells appear atypical even when no precancerous changes are present.
• Low estrogen – Reduced estrogen levels, particularly after menopause, can change the appearance of cervical cells and sometimes lead to an abnormal Pap test.
• Benign cervical inflammation – Mild irritation or inflammation caused by routine healing, sexual activity or other noncancerous factors can temporarily affect the appearance of cervical cells.
• Yeast infection – A vaginal yeast infection can produce inflammation that alters cervical cells enough to cause a mildly abnormal Pap test.

The healthcare team will consider these and other possible explanations when deciding whether additional testing is necessary.

How long does it take for atypical squamous cells to turn into cancer?

In most cases, atypical squamous cells never develop into cervical cancer, and when cancer does occur, it typically develops very slowly. Persistent infection with high-risk HPV can gradually cause precancerous changes that may take 10 to 20 years, and sometimes longer, to progress to cancer if left untreated. This slow progression gives healthcare providers many opportunities to detect, monitor and treat the abnormal cells long before cancer develops. It is also one of the main reasons Pap tests and HPV tests have been so successful at preventing cervical cancer and detecting it early when treatment is most effective. 

Will I need surgery to remove abnormal squamous cells?

Not necessarily. Most patients with atypical squamous cells do not require surgery. Many patients, especially those with ASC-US and a negative HPV test, simply need a repeat Pap test or HPV test after an appropriate follow-up interval. This watchful-waiting approach can allow the healthcare team to determine whether the cellular changes resolve naturally, which often happens without treatment.

If additional testing identifies precancerous changes that are unlikely to resolve on their own, the healthcare team may recommend a minor procedure to remove the abnormal tissue before cancer develops. Options may include:

• Loop electrosurgical excision procedure (LEEP) – Using a thin wire loop carrying a low-voltage electrical current, the physician will remove a small area of abnormal cervical tissue.
• Cone biopsy (conization) – The physician will surgically remove a cone-shaped section of cervical tissue for detailed examination and, if appropriate, treatment of precancerous changes.

These procedures are generally recommended only when diagnostic testing confirms more significant abnormalities, not simply because atypical squamous cells were identified on a Pap test.

The Moffitt Cancer Center difference for atypical squamous cells

An abnormal Pap test result can raise many questions, but it is important to keep in mind that most atypical squamous cell findings are not cancer. At Moffitt, our gynecologic specialists provide comprehensive evaluations using advanced diagnostic techniques to determine whether additional testing, monitoring or treatment is appropriate. We work closely with each patient to explain their lab results, answer questions and develop an individualized care plan based on their unique needs.

To learn more about atypical squamous cells, you can request an appointment with a specialist in Moffitt’s gynecologic clinic by calling 1-888-663-3488 or submitting a new patient registration form online. We do not require referrals.