Low-grade squamous intraepithelial lesions are precancerous lesions of the cervix. They usually regress spontaneously but can sometimes progress to invasive cancer. Regular screening for these lesions by smear of the cervix is ​​necessary.

Definition of low-grade intraepithelial malpighian lesions

Squamous intraepithelial lesions affect the cervix (structure of the female reproductive system), and more exactly one of the tissues covering it: the squamous epithelium. They result in the appearance of abnormal cells. They are said to be precancerous lesions because they can progress to cancer of the cervix.

All squamous intraepithelial lesions do not have the same degree of severity and therefore do not have the same risk of developing into cancer. This is why there are two types: low-grade squamous intraepithelial lesions and high-grade squamous intraepithelial lesions. Low-grade ones can progress to high-grade ones, which in turn can progress to cervical cancer.

The latest estimates show that low-grade squamous intraepithelial lesions:

• spontaneously regress in 57% of cases;
• persist in 32% of cases;
• progress to high-grade squamous intraepithelial lesions in 11% of cases.

It is not uncommon for health professionals to use other names for squamous intraepithelial lesions: cervical intraepithelial neoplasia of grade 1, 2 or 3. This classification into three grades depends on the thickness of the affected squamous epithelium. :

• one third of the epithelium is affected for grade 1 cervical intraepithelial neoplasia (CIN1);
• two thirds of the epithelium is affected for grade 2 cervical intraepithelial neoplasms (CIN2);
• the entire epithelium is affected for grade 3 cervical intraepithelial neoplasia (CIN3).

To be found among the different names, low-grade squamous intraepithelial lesions correspond to CIN1 while high-grade squamous intraepithelial lesions correspond to CIN2 and CIN3.

Causes of low-grade squamous intraepithelial lesions

The most common and most documented cause of low-grade squamous intraepithelial lesions is human papillomavirus (HPV) infection. They are very widespread and very contagious viruses. Transmission occurs primarily through intimate, skin-to-skin contact, even without sexual intercourse. 

Persons concerned

Squamous intraepithelial lesions can affect many women because human papillomavirus (HPV) infections are common. It is estimated that 75% of the sexually active population will be infected with papillomavirus during their lifetime.

Diagnosis of low-grade intraepithelial malpighian lesions

Low-grade squamous intraepithelial lesions are detected by cervico-uterine smear. This is a sample of cells from the surface of the cervix for analysis. The smear is recommended every three years, after two normal smears spaced one year apart, for all women aged 25 to 65 years who have or have had sex.

Low-grade intraepithelial malpighian lesions are asymptomatic, i.e., with no apparent signs. Their presence can only be reported from a microscopic examination of cervical cells, hence the importance of regular cervico-uterine smear screening.

If low-grade squamous intraepithelial lesions are identified, more regular medical surveillance is implemented. Control Pap smears can be done every year. The objective is to identify any evolution from low-grade squamous intraepithelial lesions to high-grade lesions.

The prevention of low-grade squamous intraepithelial lesions and their complications relies primarily on vaccination against human papillomavirus (HPV) infections and screening for lesions by cervico-uterine smear. It is also recommended to use a condom during sex.