High grade squamous intraepithelial lesion (HSIL) of the vulva

by Emily Goebel, MD FRCPC
June 1, 2022

What is high grade squamous intraepithelial lesion (HSIL) of the vulva?

High grade squamous intraepithelial lesion (HSIL) of the vulva 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 addition to the vulva, HSIL commonly involves the cervix and vagina. In both women and men, HSIL may also involve the anal canal and peri-anal skin.

How does high grade squamous intraepithelial lesion of the vulva start?

High grade squamous intraepithelial lesion (HSIL) develops after the specialized squamous cells on the surface of the vulva become infected by human papillomavirus (HPV). Infected cells show an abnormal pattern of development called dysplasia.

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

High grade squamous intraepithelial lesion (HSIL) of the vulva is not a type of cancer although patients with HSIL are at increased risk for developing a type of vulvar 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.

How is the diagnosis of high grade squamous intraepithelial lesion of the vulva made?

The diagnosis of HSIL of the vulva is usually made after a small sample of tissue is removed in a procedure called a biopsy. The entire area of disease with then be completely in a larger surgical procedure called an excision or vulvectomy.

What is p16 and why do pathologists test for it?

Cells infected with high-risk types of human papillomavirus (HPV) produce large amounts of a protein called p16. Your pathologist may perform a test called immunohistochemistry to look for p16 inside the abnormal cells in the tissue sample. This will confirm the diagnosis of HSIL and rule out other conditions that can look like HSIL under the microscope. Almost all cases of HSIL are positive or reactive for p16.

Margins

A margin is any tissue that has to be cut by the surgeon in order to remove the tumour from your body. A negative margin means that no HSIL cells were seen at the cut edge of the tissue. In contrast, a positive margin means that HSIL cells were seen at the cut edge of the tissue. A positive margin increases the risk that the tumour will grow back in that location. Margins will only be described in your report after the entire tumour has been removed.