Pap test results -

High grade squamous lesion (HSIL)

This article was last reviewed and updated on August 28, 2019
by Adnan Karavelic, MD FRCPC

Quick facts:

  • High grade squamous intraepithelial lesion (HSIL) is a pre-cancerous disease that develops in the cervix.

  • HSIL is caused by a virus called human papillomavirus (HPV).

  • If left untreated, patients with HSIL are at high risk for developing a cancer of the cervix called squamous carcinoma.

The normal cervix

The cervix is part of the female genital tract. It is found at the bottom of the uterus where it forms an opening into the endometrial cavity. The narrow passage that runs through the cervix from the endometrium to the vagina is called the endocervical canal. 

The part of the cervix inside the vagina is called the exocervix. It is covered by special cells called squamous cells. These cells form a barrier called the epithelium that protect the cervix. The endocervical canal is covered by different kinds of cells that connect to form endocervical glands. The area of the cervix where the exocervix meets the endocervical canal is called the transformation zone. 

Why is this important? Most cancers of the cervix start in the transformation zone. 

Why is the Pap test performed?

The Pap test is a screening test designed to look for pre-cancerous and cancerous cells in the cervix. Read our introduction article to learn more about the Pap test.


What is high grade squamous intraepithelial lesion (HSIL)?

HSIL is a pre-cancerous condition that starts from the squamous cells on the surface of the cervix. It is called a pre-cancerous condition because, over time, it can turn into a type of cancer called squamous cell carcinoma. Most cases of HSIL are caused by a virus called human papilloma virus (HPV).

Another name for HSIL is moderate to severe squamous dysplasia

Why is this important? Not all women with HSIL will develop cancer. However, to reduce the risk, most patients are offered treatment to remove the disease. 

How do pathologists make the diagnosis of HSIL?

When examined under the microscope, the abnormal squamous cells in LSIL are darker and larger than normal squamous cells. The genetic material which is found inside the nucleus of the cell may also be grouped together or coarse. The abnormal cells in HSIL are usually in small groups or as single cells. Some normal squamous cells may also be seen at the same time. 

What happens after HSIL is diagnosed on Pap test?

After being diagnosed with HSIL your doctor should refer you to a specialist who will perform a colposcopy. A colposcopy allows your doctor to see the entire outer surface of the cervix. 

During the colposcopy, the doctor will be looking for any areas that look abnormal on the surface of the cervix. If an abnormality is found, the doctor may decide to take a small biopsy, to confirm the diagnosis of HSIL and to look for squamous cell carcinoma. Your doctor may also take a small sample of tissue from the endocervical canal and endometrium. 

Why is this important? All patients with HSIL should be followed closely or offered treatment to remove the disease. 

There are several treatment options available:

  • Laser ablation – A laser is used to remove the abnormal squamous on the surface of the cervix.

  • Loop electrosurgical excision procedure (LEEP) – A special type of knife is used to remove the tissue from the surface of the cervix.

  • Large loop excision of the transformation zone (LLETZ) – Similar to LEEP (above).

  • Cold knife cone biopsy – Similar to LEEP (above).

  • Hysterectomy – In this procedure the entire uterus and cervix is removed. This procedure is usually only performed when squamous cell carcinoma is found and for large tumours. 

There are many factors to consider when deciding which treatment option is best for you. Talk to your doctor about the options available.

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