Low grade squamous intraepithelial lesion (LSIL)
This article was last reviewed and updated on October 31, 2018
by Emily Goebel, MD FRCPC
Low grade squamous intraepithelial lesion (LSIL) is a non-cancerous condition that develops in the vagina.
LSIL is caused by a virus called human papillomavirus (HPV) which infects cells on the inner surface of the vagina.
LSIL can turn into a cancer over time although the risk is very low.
The normal vagina
The vagina is part of the female genital tract. It forms a canal that starts at the cervix and ends at the vulva on the outside of the body. The vagina is lined by special cells called squamous cells that form a barrier on the inner lining of the vagina called the epithelium. The tissue beneath the epithelium is called the lamina propria and contains blood vessels and connective tissue. Together, the epithelium and lamina propria are called mucosa.
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 inner surface of the vagina. 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.
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 vagina will return to normal.
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.
LSIL was previously called vaginal intraepithelial neoplasia (VAIN1) and some reports may still use this terminology.
The diagnosis of LSIL is usually made after a small sample of tissue is removed in a procedure called a biopsy. Biopsies from the vulva and cervix may also be taken to look for a similar condition in those areas. Additional treatment is not always required.