Your diagnosis

High grade squamous intraepithelial lesion of the cervix

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

by Jason Wasserman, MD PhD FRCPC, updated December 24, 2020

high grade squamous intraepithelial lesion cervix

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 anatomy of the cervix

The cervix is part of the female genital tract. It is found at the bottom of the uterus where it forms an opening and a canal into the endometrial cavity of the uterus.

The outer surface of the cervix is lined by two types of cells that form a barrier called the epithelium. The first part of the cervix is called the exocervix and it is lined by squamous cells. The second part of the cervix is called the endocervical canal and it is lined by rectangular shaped cells which connect together to make small structures called glands.

The tissue below the epithelium is called the stroma and is made up of connective tissue and blood vessels.

What is high grade squamous intraepithelial lesion (HSIL)?

High grade squamous intraepithelial lesion (HSIL) is a pre-cancerous disease that develops in the cervix. 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 stroma below, the diagnosis changes to squamous cell carcinoma. The spread of abnormal cells from the epidermis into the stroma is called invasion.

The abnormal cells in HSIL are unable to spread to tissues outside of the cervix or to other parts of the body such as lymph nodes.

What causes high grade squamous intraepithelial lesion?

Almost all cases of HSIL and squamous cell carcinoma in the cervix are a result of the normal squamous cells becoming infected with a high risk type of human papillomavirus (HPV).​ The most common types of high risk HPV to cause HSIL are HPV-16 and HPV-18.

How do pathologists make this diagnosis?

The diagnosis of HSIL is usually made after a small tissue sample is removed during a Pap test or a biopsy. The diagnosis can also be made when part or all of the cervix is removed for another reason.

When examined under the microscope, the abnormal squamous cells in HSIL are darker and larger than normal squamous cells. The chromatin (genetic material) which is found inside the nucleus of the cell may be described as coarse or vesicular which means it is divided into small groups.

In a Pap test the abnormal cells are often grouped together although your pathologist may also see single abnormal cells on the slide. In a tissue biopsy, the abnormal cells are usually found throughout the epithelium. Unlike normal, healthy squamous cells, the abnormal cells do not become smaller and flatter as they move from the bottom of the epithelium to the top.

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 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.​

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.

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

​Extent of disease

Larger samples of tissue are usually sent for pathological examination as a single piece of tissue and the tissue is then divided into multiple sections before being examined under the microscope. Your pathologist will describe the number of pieces (or ‘blocks’ as they are often called) that show HSIL in your report.

For example, your report may say “3 out of 14 blocks are positive for high grade squamous intraepithelial lesion (HSIL)” which means that 3 out of the 14 pieces of tissue examined show the disease.


A margin is any tissue that has to be cut by the surgeon in order to remove the tumour from your body. If you underwent a surgical procedure to remove the entire tumour from your body, your pathologist will examine the margin closely to make sure there are no cancer cells at the cut edge of the tissue.


The number and type of margins will depend on the type of procedure performed to remove the tumour from your body. Typical margins include:

  • Endocervical margin – This is where the cervix meets the inside of the uterus.
  • Ectocervical margin – This is the bottom of the cervix, closest to the vagina.
  • Stromal margin – This is the tissue inside the wall of the cervix.

A margin is considered positive when HSIL is seen at the edge of the cut tissue. Finding HSIL at the margin increases the risk that the tumour will grow back in that location.

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