Definition

An abnormal growth of squamous cells that forms on the surface of certain organs, such as the cervix, vagina, vulva, anus, penis, or back of the throat. Squamous cells are thin, flat cells that look like fish scales under a microscope. SILs may be low grade or high grade, depending on how abnormal the cells look under a microscope and how much of the tissue is affected. They are usually caused by chronic infection with certain types of human papillomavirus (HPV) and are found when a Pap test or biopsy is done. If not treated, some SILs may become cancer and spread into nearby normal tissue. Also called squamous intraepithelial lesion.