High-grade squamous intraepithelial lesion (HSIL) is a pre-cancerous, sexually transmitted disease caused by infection with a virus called human papillomavirus (HPV). This condition may affect both women and men. In women, HSIL commonly involves the cervix, vulva, or vagina. In both women and men, LSIL may also involve the anal canal and peri-anal skin. Your doctor may perform a test called a Pap smear or biopsy to look for HSIL and the diagnosis is made after the tissue sample is examined under the microscope by a pathologist.
HSIL develops after the specialized squamous cells on the surface of the tissue in this region become infected by the virus. Infected cells show an abnormal pattern of development called dysplasia. HSIL is not cancer although patients with HSIL are at increased risk for developing a type of cancer called squamous cell carcinoma. For this reason, most patients with HSIL are offered treatment to remove the area of abnormal tissue. Low-grade squamous intraepithelial lesion (LSIL) is a related condition that is also caused by HPV. However, compared to HSIL, the risk of developing cancer from LSIL is much lower.