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Low-grade Squamous Intraepithelial Lesion

Low-grade Squamous Intraepithelial Lesion

A low-grade squamous intraepithelial lesion is a precancerous lesion. It refers to the early changes in the squamous cells that are present on the surface of the ectocervix. The following write-up provides information on the causes, risk factors, diagnosis, and treatment of this condition.
Dr. Sumaiya Khan
Last Updated: Apr 16, 2018
Squamous cells are a type of epithelial cells that are present in various parts of the body. These flat, scale-like cells are present on the lips and in the mouth. These are also present in the cervix, which is the lower part of the uterus that connects it to the vagina.

The term 'squamous intraepithelial lesion' (SIL) refers to the abnormal changes in squamous cells that form the surface of the cervix. Also referred to as cervical intraepithelial neoplasia (CIN) or cervical dysplasia, these squamous intraepithelial lesions are considered to be the early stage of precancerous lesions that may or may not lead to squamous cell carcinoma of the cervix.

The abnormal changes in the shape, size, and the number of squamous cells on the surface of the cervix are categorized into low-grade squamous intraepithelial lesions (LGSIL) and high-grade squamous intraepithelial lesions (HGSIL).

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Squamous Intraepithelial Lesions

While the low-grade lesions are more likely to affect women in the age group of 25 to 35 years, the high-grade lesions may develop in women who are in the age group of 30 to 40 years. In case of high-grade lesions, the cells appear to be very different from the normal cells. These lesions are more likely to turn malignant, and affect the deeper layers of the cervix with time.

While the low-grade lesions are indicative of mild cervical dysplasia or CIN I, the high-grade lesions are indicative of moderate cervical dysplasia (CIN II), severe cervical dysplasia (CIN III), or carcinoma in situ (CIS).

It is believed that there is a 12-16% chance of a low-grade lesion progressing into severe cervical dysplasia, whereas 20% of high-grade lesions could progress to invasive cervical carcinoma in the absence of treatment.

Contributory Factors

Certain risk factors are associated with the development of low-grade squamous intraepithelial lesions. Women who are more susceptible include:

Those who smoke
Women who have multiple sexual partners
Women who become sexually active at an early age
Women who are immunodeficient
Women who are infected with a high-risk strain of human papillomavirus (HPV)

The low-grade lesions are often associated with an infection with the human papillomavirus (HPV). HPV refers to a group of viruses that are associated with the development of genital warts.

HPV 16 and 18 are high-risk strains that are associated with the development of cervical cancer. This virus can get transmitted through skin-to-skin contact. Sexual intercourse with an infected person can cause the virus to spread.


Pap smear is a test that involves the microscopic examination of cells that have been scraped from the ectocervix region or the opening of the cervix. Atypical or abnormal cells can be detected on the Pap smear.

The term 'atypical squamous cells of undetermined significance' (ASCUS) means that a few changes are seen in some cells. These changes are not considered to be of a serious nature, but the doctor may recommend another Pap smear after some time, or HPV testing to find out if the changes are due to infection with HPV. Both low-grade and high-grade squamous epithelial lesions can be detected on a PAP smear.

Since cervical dysplasia is asymptomatic, it is usually detected incidentally on a routine Pap smear test. In case of a high-grade lesion, the chances of a precancerous lesion turning into a malignant growth soon are high, when compared to a low-grade lesion. Low-grade lesions are usually transient and may resolve on their own.

If a low-grade lesion is detected, diagnostic procedures such as colposcopy and biopsy need to be conducted. Those who come under the high-risk group for cervical cancer are usually asked to undergo serial Pap smear tests every 4-6 months.

Spontaneous regression (low-grade lesion on Pap smear followed by a subsequent normal Pap smear conducted about 11.5 months later) has been noted in 50% to 60% of cases. In 20% to 30% of the cases, the low-grade lesion may progress to a high grade lesion.

Treatment and Prevention

Most doctors prefer to follow the 'wait and watch' philosophy while dealing with LGSIL. The reason why this condition needs to be closely monitored is because these lesions could sometimes progress into severe dysplasia.

During the follow-up, doctors tend to use diagnostic methods such as colposcopy and biopsy to check for abnormalities. If abnormal changes in the cells are observed, and the lesion seems to be turning into a high-grade lesion, then the doctor may choose to destroy or remove the abnormal cells with the help of:

Laser therapy
Cryotherapy (destruction of abnormal cells by freezing them)
Cold knife conization (excision of a cone-shaped wedge of tissue from the cervix with a scalpel)
Loop electrosurgical excision procedure (removal of abnormal cervical cells with a wire loop through which electric current is passed)

At times, LGSIL could transgress into high-grade squamous intraepithelial lesions, which in turn could eventually lead to cervical cancer. It is therefore recommended that precautionary measures be followed by women with a persistent HPV infection or family history of cervical cancer. Having a single sex partner and practicing safe sex considerably reduces the risk. Getting vaccinated for HPV after the onset of puberty, or before the age of 25 years is another preventive measure. Since smoking is a risk factor, it would be best to refrain from smoking.

Squamous epithelial lesions don't always cause noticeable symptoms. Hence, it is of paramount importance that women regularly get pap smear tests done. This is especially applicable to women who are at a greater risk of developing cervical cancer.

Disclaimer: The information provided in this article is solely for educating the reader. It is not intended to be a substitute for the advice of a medical expert.