Vulva -

Low grade squamous intraepithelial lesion (LSIL)

This article was last reviewed and updated on October 31, 2018
by Emily Goebel, MD FRCPC

Quick facts:

  • Low grade squamous intraepithelial lesion (LSIL) is a non-cancerous condition that develops on the vulva.

  • LSIL is caused by a virus called human papillomavirus (HPV) that infects the cells on the surface of the vulva.


The normal 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 made up of squamous cells. The tissue beneath the epidermis is called the dermis, it contains blood vessels and connective tissue.
What is low grade squamous intraepithelial lesion (LSIL)?

Low grade squamous intraepithelial lesion (LSIL) is a non-cancerous disease that develops from the squamous cells on the vulva. LSIL is caused by a virus called human papillomavirus (HPV) that infects the squamous cells. Once inside the cell, HPV changes the cell and prevents it from developing normally. Pathologists call this change dysplasia.

Although LSIL is considered non-cancerous disease, there is a very small risk that it will turn into a cancer over time. However, for most patients with LSIL, the immune system will remove the infected cells and the vulva will return to normal.

The specific HPV virus associated with LSIL is typically a low risk type of HPV.  Cells infected with low risk HPV are much larger than normal squamous cells and are called koilocytes

LSIL was previously called vulvar intraepithelial neoplasia (VIN1) and some reports may still use this terminology.

A similar condition with the same name (LSIL) can develop in the cervix or vagina.

The diagnosis of LSIL is usually made after a small sample of tissue is removed in a procedure called a biopsy. The affected areas are usually treated with topical or laser therapy.  


A larger biopsy or excision  may be performed to look for features of a related, but more serious condition, called high grade intraepithelial lesion (HSIL) or squamous cell carcinoma.

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