By Jason Wasserman MD PhD FRCPC
April 13, 2023
Low grade squamous intraepithelial lesion (LSIL) is a precancerous change that commonly involves the cervix, vagina, vulva, penis, or anal canal. This condition may affect both women and men.
LSIL is caused by infection with human papillomavirus (HPV). The virus infects squamous cells found on the surface of the cervix, vagina, vulva, penis, or anal canal which over time develop genetic changes that lead to LSIL.
LSIL is a precancerous condition which means it can turn into a type of cancer called squamous cell carcinoma over time. LSIL can also change into a more advanced precancerous condition called high grade squamous intraepithelial lesion (HSIL). However, it is important to know that the risk of LSIL turning into cancer is very low, and for most people with LSIL, the immune system will remove the infected cells and the tissue will return to normal over time.
The diagnosis is made after a Pap smear or biopsy is performed and the tissue is sent to a pathologist for examination under the microscope. Compared to normal, healthy squamous cells, the squamous cells in LSIL are larger and darker and the nucleus (the part of the cell that holds the genetic material) often has an irregular shape. Pathologists sometimes call these cells koilocytes or use the term koilocytic change to describe these microscopic features. If immunohistochemistry is performed, the cells in LSIL are typically negative for p16.