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    Low-Grade Squamous Intraepithelial Lesion: When Pap Smear Results Are Abnormal

    Published 16 March 2020
    Fact Checked
    Eugenia Tikhonovich, MD
    Reviewed by Eugenia Tikhonovich, MD, Obstetrician-Gynecologist, Medical Consultant
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    The tissue covering your cervix is comprised of squamous cells. A routine Pap smear screening involves taking a cell scraping for microscopic examination. When these cells appear abnormal, they’re classified as squamous intraepithelial lesions (SILs).

    What is LSIL?

    You may hear low-grade squamous intraepithelial lesion (LSIL) being referred to as LGSIL or a low-grade abnormal Pap smear. Unusual cell growth is caused by certain strains of the human papillomavirus (HPV). Upon microscopic examination, these squamous cells will display mild dysplasia or abnormalities.

    The presence of intraepithelial lesions is extremely common in Pap screenings and does not indicate cancer. In fact, the overall likelihood of patients with LSIL getting cancer is less than 1%.

    Oftentimes, your body’s immune system kicks in and fights off HPV on its own, and LSIL resolves itself. However, if LSIL progresses into HSIL, precancer, or cancer, it could invade healthy tissues nearby.

    LSIL vs. HSIL

    Atypical squamous cells, or ASC, are classified into one of four categories:

    • Low-grade squamous intraepithelial lesions (LSIL)
    • High-grade squamous intraepithelial lesions (HSIL)
    • Atypical glandular cells (AGC)
    • Invasive cervical cancer

    In contrast to LSIL, HSIL creates significant abnormalities, known as moderate or severe dysplasia. Although HSIL cells can theoretically disappear without treatment, it’s far less likely.

    Left untreated, HSIL is capable of developing into cervical cancer. So when your doctor detects these squamous intraepithelial lesions, they’ll probably recommend further screening and treatment.

    Connection between LSIL, HSIL, and cancer

    A diagnosis of LSIL or HSIL doesn’t necessarily equal cancer. Plus, the presence of squamous intraepithelial lesions on your Pap smear doesn’t increase your chances of precancer or cancer.

    Instead, the main culprit behind cervical cancer is infection with HPV. Several types of HPV have been linked to cancer of the vulva, vagina, penis, anus, and cervix. (In rare cases, high-risk HPV strains are also associated with head and neck cancer.)

    Note that cervical cancer is typically caused by either HPV 16 or 18. When a cell becomes infected, it shows abnormalities under microscopic examination. Severe and untreated abnormalities have the potential to eventually become precancer or cancer.

    LSIL symptoms

    Unfortunately, the existence of precancer cells in your body is usually asymptomatic. Most women remain unaware of LSILs or HSILs until they receive their Pap results. That’s why it’s important to follow routine screening guidelines appropriate for your age and other factors. Check with your provider for more details.

    Is LSIL treatable?

    The good news is that both LSIL and HSIL can be successfully treated, especially when caught early. Remember that any type of abnormal Pap smear results will require follow-up appointments. Aside from your age, the presence of HPV determines what your care plan will look like. Most doctors base their guidelines on recommendations from the American Congress of Obstetricians and Gynecologists (ACOG).

    Treatment options for low-grade squamous intraepithelial lesion

    For most, LSILs do not warrant immediate medical attention. The standard approach to LSIL treatment for patients between 21 and 24 years old is getting another Pap smear and HPV test in one year. 

    If you’re 25 or older, a colposcopy, which is an extensive visual examination of your cervix, is suggested. It may or may not be accompanied by a biopsy, or removal of a small piece of tissue for additional testing. It largely depends on the presence (or absence) of HPV and past Pap results. Biopsies are critical in the search for precancer or cancer cells.

    Treatment options for high-grade squamous intraepithelial lesion

    As expected, methods for addressing HSILs are different from LSILs. Regardless of your age, waiting a full year for rescreening is not recommended. Currently, ACOG guidelines advise performing a colposcopy and potential excision of intraepithelial lesions. Once again, further testing is conducted to look for precancer or cancer cells.

    Are you now wondering, “how fast does HSIL turn into cancer?” There’s really no definitive answer. HSIL doesn’t always progress into cancer, but it is capable of it. In some cases, it might take as long as 10 years or more; in other cases, it could happen much more quickly. But with proper diagnosis and management, HSIL does not have to develop into cancer at all.


    Naturally, each time you go in for a routine Pap smear, you’re hoping to receive a clean bill of health. If your doctor does find LSIL or any type of intraepithelial lesion or malignancy, there’s no need to panic.

    It’s very rare that LSIL immediately points to cervical cancer. While your doctor will ask you to do additional screenings, rest assured that the occasional abnormal Pap result is very common. 

    For many patients, LSIL fully resolves on its own. And even if it doesn’t, expert treatment and care can still minimize the impact LSIL has on your overall health.

    History of updates

    Current version (16 March 2020)

    Reviewed by Eugenia Tikhonovich, MD, Obstetrician-Gynecologist, Medical Consultant

    Published (16 March 2020)

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