This article will help you read and understand your pathology report for high grade squamous intraepithelial lesion (HSIL) of the vagina.
by Emily Goebel MD FRCPC, updated December 24, 2020
The vagina is part of the female genital tract. It forms a canal that starts at the cervix and ends at the vulva on the outside of the body. The vagina is lined by special cells called squamous cells that form a barrier on the inner lining of the vagina called the epithelium. The tissue beneath the epithelium is called the lamina propria and contains blood vessels and connective tissue. Together, the epithelium and lamina propria are called mucosa.
High grade squamous intraepithelial lesion (HSIL) is a pre-cancerous disease that develops in the vagina. 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 epithelium. If the abnormal cells spread beyond the epithelium and into the lamina propria below, the diagnosis changes to squamous cell carcinoma. The spread of abnormal cells from the epidermis into the lamina propria is called invasion.
HSIL of the vagina was previously called to as vaginal intraepithelial neoplasia (VAIN2-3) and some reports may still use this terminology.
The diagnosis of HSIL is usually made after a small sample of tissue is removed in a procedure called a biopsy. A larger surgical procedure (for example, an excision or vaginectomy) is later performed to remove the disease and look for abnormal cells in the lamina propria.
HSIL is caused by a virus called human papillomavirus (HPV) that infects the squamous cells in the epithelium. There are many types of HPV virus and most cases of HSIL are caused by the high risk types HPV-16 and HPV-18.
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.
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.