Squamous intraepithelial lesion

LEEP cone biopsy displaying normal cervical epithelium (far left) progressing to borderline koilocytosis, to LSIL, and to HSIL (far right).

A squamous intraepithelial lesion (SIL) is an abnormal growth of squamous cells on the surface of the cervix; normal squamous cells make up the normal epithelium of the cervix. This lesion can progress to cervical cancer and can be diagnosed using a Pap smear or a colposcopy. It can be treated by using methods that remove the abnormal cells, allowing normal cells to grow in their place. In the Bethesda system, the cytology can be graded as LSIL (low-grade squamous intraepithelial lesion) or HSIL (high-grade squamous intraepithelial lesion).