What Is a Low-Grade Squamous Intraepithelial Lesion?

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  • Written By: Geisha A. Legazpi
  • Edited By: Allegra J. Lingo
  • Last Modified Date: 15 October 2019
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Low-grade squamous intraepithelial lesions (LGSIL or LSIL) are abnormal growths in the surface layer of the cervix, particularly in the transformation zone. They can be detected by the Papanicolaou (Pap) smear test, which checks for changes in cervix cells and increases the changes of early detection of malignancy. Since the introduction of the Pap smear in the mid-20th century, cases of cervical cancer are diminishing, although it remains a leading cause of death among women in developing countries.

Samples taken from a Pap smear are examined under a microscope. The examiner looks for a low-grade squamous intraepithelial lesion, which is characterized by dysplasia. It is important to discover precancerous lesions because they can be treated to prevent progression to full-blown cancer. The Bethesda system classifies precancerous cervical cells into low-grade squamous intraepithelial lesion and high-grade squamous intraepithelial lesion (HSIL). If not properly managed, about 20% of low-grade lesions can progress into their high-grade counterparts, and 1% of these become invasive cancers.

Dysplasia is a term that refers to the lack of uniformity among cells of the same origin and loss of their architectural orientation. In cervical dysplasia, the nuclei of the cells appear hyperchromatic or denser than normal, and they are distinctly large relative to the cell size. Dysplastic cells look different from neighboring normal cells. They exhibit pleiomorphism, which simply means they have variable shapes.


The occurrence of a low-grade squamous intraepithelial lesion is associated with the human papillomavirus (HPV) infection. According to studies, the risk of LSIL and HSIL depends on exposure to high-risk human papillomaviruses. The subtypes, which are considered low risk, are HPV 6 and 11, while those considered high risk are HPV 16 and 18. Like other HPV variants, these viruses are transferred through sexual contact. Having multiple sexual partners, being very young at the first sexual contact, being in the lower socioeconomic strata, and having a persistent infection with the high-risk HPV subtypes are considered the main risk factors for LSIL and HSIL formation.

To provide a definitive diagnosis of low-grade squamous intraepithelial lesion, the cervix is visualized through a microscope using a method called colposcopy. A biopsy may be done to rule out the possibility of malignancy. The goal of LSIL treatment is to kill the abnormal cells on the cervical surface. Cryotherapy, or the application of very low temperatures to the cervical surface, is often performed. When the abnormal cells are spread over a wide area, the whole area may be removed to decrease the risk of cancer.


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