by Emily Goebel, MD FRCPC
January 12, 2023
Low grade squamous intraepithelial lesion (LSIL) of the vulva is a non-cancerous, sexually transmitted disease. This condition may affect both women and men. In addition to the vulva, LSIL can also affect the cervix and vagina. In both women and men, LSIL may also involve the anal canal and peri-anal skin. Another name for this condition is vulvar intraepithelial neoplasia (VIN).
LSIL of the vulva is casued by human papillomavirus (HPV). The virus infects squamous cells on the surface of the vulva. Over time the infected cells show an abnormal pattern of development called dysplasia.
LSIL of the vulva is not a type of cancer but there is a very small risk that it will turn into a type of vulvar cancer called squamous cell carcinoma over time. However, for most patients with LSIL, the immune system will remove the infected cells and the tissue will return to normal. High-grade squamous intraepithelial lesion (HSIL) is a related condition that is also caused by HPV. Compared to LSIL, the risk of developing cancer from HSIL is much higher.
The diagnosis of LSIL of the vulva is usually made after a small sample of tissue is removed in a procedure called a biopsy. The affected areas are usually treated with topical or laser therapy. A larger biopsy or excision may be performed to look for features of related, but more serious conditions called high-grade intraepithelial lesion (HSIL) and squamous cell carcinoma.
LSIL starts when the squamous cells on the surface of the vulva become infected with human papillomavirus (HPV). When examined under the microscope, the infected squamous cells in LSIL are much larger than normal squamous cells and the nucleus of the cell (the part that holds the genetic material) is darker and surrounded by a clear space called a halo. Pathologists describe these infected cells as koilocytes.