High grade squamous intraepithelial lesion of the vulva

This article will help you read and understand your pathology report for high grade squamous intraepithelial lesion of the vulva.

by Emily Goebel, MD FRCPC, reviewed on September 19, 2020

Quick facts:

• High grade squamous intraepithelial lesion (HSIL) is a pre-cancerous disease that develops on the vulva.
• HSIL is caused by a virus called human papillomavirus (HPV).
• If left untreated, patients with high grade squamous intraepithelial lesion are at high risk for developing a cancer called squamous carcinoma.

The anatomy of the vulva

The vulva is the external part of the female genital tract.  It forms the opening of the vagina and includes the mons pubis, labia majora, labia minora and clitoris. The vulva is composed of skin. The surface of the skin is called the epidermis and is mostly made up of squamous cells. The tissue beneath the epidermis is called the dermis, it contains blood vessels and connective tissue.

What is high grade squamous intraepithelial lesion?

High grade squamous intraepithelial lesion (HSIL) is a pre-cancerous disease that develops in the vulva. HSIL is called a pre-cancerous disease because over time it can turn into a type of cancer called squamous cell carcinoma.

Unlike squamous cell carcinoma, the abnormal cells in HSIL are found only in the epidermis. If the abnormal cells spread beyond the epidermis and into the dermis below, the diagnosis changes to squamous cell carcinoma. The spread of abnormal cells from the epidermis into the dermis is called invasion.

Other names for this condition

High grade squamous intraepithelial lesion (HSIL) was previously called vulvar intraepithelial neoplasia (VIN2-3) and some reports may still use this name.

What causes high grade squamous intraepithelial lesion?

HSIL is caused by a virus called human papillomavirus (HPV) that infects the squamous cells in the epidermis. There are many types of HPV virus and the most causes of HSIL are caused by the high risk types HPV-16 and HPV-18.

How do pathologists make this diagnosis?

The diagnosis of HSIL 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​?

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. 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 which means your pathologist saw the p16 protein in the abnormal cells.

What to look for in your report after the tumour has been removed

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.