December 13, 2023


Koilocytes are abnormal squamous cells that have been infected by human papillomavirus (HPV). They are commonly seen in conditions caused by HPV including low grade squamous intraepithelial lesion (LSIL) and high grade squamous intraepithelial lesion (HSIL). Koilocytes are often observed in tissues, such as the cervix, vagina, penis, anus, and oral cavity, where HPV infections can occur.

When examined under the microscope koilocytes are larger than normal squamous cells and the nucleus of the cell (the part that holds the genetic material) is often darker and more convoluted. The nucleus may also be surrounded by a white space called a halo. The presence of koilocytes is strongly suggestive of HPV infection, and their identification is important in the diagnosis of HPV-related lesions.

About this article

This article was written by doctors to help you read and understand your pathology report. Contact us if you have questions about this article or your pathology report. For a complete introduction to your pathology report, read this article.

Related articles

Low grade squamous intraepithelial lesion (LSIL)
High grade squamous intraepithelial lesion (HSIL)
Human papillomavirus (HPV)

Other helpful resources

Atlas of pathology
A+ A A-