Low grade squamous intraepithelial lesion of the vulva

by Emily Goebel, MD FRCPC
December 18, 2023

Low grade squamous intraepithelial lesion (LSIL) of the vulva is an abnormal growth caused by infection with human papillomavirus (HPV). The abnormal growth seen in LSIL is an example of dysplasia. In addition to the vulva, LSIL can also affect the vagina and cervix. In both women and men, LSIL may also involve the anal canal and peri-anal skin. Another name for this condition is vulvar intraepithelial neoplasia 1 (VIN1).

The virus infects squamous cells found on the surface of the vulva which over time develop genetic changes that lead to LSIL. The squamous cells form a thin layer of tissue called the epithelium. The term “intraepithelial” means that the abnormal cells in LSIL are still located entirely within the epithelium.

Is low grade squamous intraepithelial lesion of the vulva a type of cancer?

LSIL of the vulva is not a type of cancer but there is a small risk that it will turn into a type of vulvar cancer called squamous cell carcinoma over time. However, for most patients with LSIL, the immune system will remove the infected cells and the tissue will return to normal. High-grade squamous intraepithelial lesion (HSIL) is a related condition that is also caused by HPV. Compared to LSIL, the risk of developing cancer from HSIL is much higher.

What does low grade squamous intraepithelial lesion of the vulva look like under the microscope?

LSIL starts when the squamous cells on the surface of the vulva become infected with human papillomavirus (HPV). When examined under the microscope, the infected squamous cells in LSIL are much larger than normal squamous cells and the nucleus of the cell (the part that holds the genetic material) is darker and surrounded by a clear space called a halo. Pathologists describe these infected cells as koilocytes.

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.

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

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