Low grade squamous intraepithelial lesion (LSIL)
This article was last reviewed and updated on October 8, 2018
by Jason Wasserman, MD PhD FRCPC
Low grade squamous intraepithelial lesion (LSIL) is a non-cancerous condition that develops in the cervix.
LSIL is caused by a virus called human papillomavirus (HPV) which infects cells on the surface of the cervix.
LSIL can turn into a cancer over time although the risk is very low.
The normal cervix
The cervix is part of the female genital tract. It is found at the bottom of the uterus where it forms an opening and a canal into the endometrial cavity of the uterus.
The outer surface of the cervix is lined by two types of cells that form a barrier called the epithelium. The first part of the cervix is called the exocervix and it is lined by squamous cells. The second part of the cervix is called the endocervical canal and it is lined by rectangular shaped cells which connect together to make small structures called glands.
The tissue below the epithelium is called the stroma and is made up of connective tissue and blood vessels.
What is low grade squamous intraepithelial lesion (LSIL)?
Low grade squamous intraepithelial lesion (LSIL) is a non-cancerous disease that develops from the squamous cells on the surface of the cervix.
Although LSIL is considered non-cancerous disease, there is a very small risk that it will turn into a cancer over time. However, for most patients with LSIL, the immune system will remove the infected cells and the cervix will return to normal.
Why is this important? The abnormal cells in LSIL are unable to spread into the tissues outside of the cervix or to other parts of the body such as lymph nodes.
What causes low grade squamous intraepithelial lesion?
LSIL is caused by a virus called human papillomavirus (HPV) that infects the squamous cells. Once inside the cell, HPV changes the cell and prevents it from developing normally. Pathologists call this change dysplasia.
The specific HPV virus associated with LSIL is typically a low risk type of HPV. Cells infected with low risk HPV are much larger than normal squamous cells and are called koilocytes.
How do pathologists make this diagnosis?
The diagnosis of LSIL is usually made after a small sample of tissue is removed in a pap smear or a procedure called a biopsy. A larger biopsy may be performed later to look for a related but more serious condition called high grade intraepithelial lesion (HSIL) or squamous cell carcinoma.