Low-grade squamous intraepithelial lesion of the cervix

What is low-grade squamous intraepithelial lesion?

Low-grade squamous intraepithelial lesion (LSIL) is a non-cancerous disease that develops from the squamous cells on the surface of the cervix. Although LSIL is considered a non-cancerous disease, there is a very small risk that it will turn into cancer called squamous cell carcinoma over time. However, for most patients with LSIL, the immune system will remove the infected cells and the cervix will return to normal. Because LSIL is a non-cancerous disease, the abnormal cells are unable to spread into the tissues outside of the cervix or to other parts of the body such as lymph nodes.

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 causes low-grade squamous intraepithelial lesion?

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. 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.

How do pathologists make this diagnosis?

The diagnosis of LSIL 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 LSIL 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. While normal squamous cells have one nucleus, some of the abnormal cells in LSIL may have two nuclei. The abnormal cells found in LSIL are sometimes called koilocytes.

low grade squamous intraepithelial lesion cervix

What happens after LSIL is diagnosed on Pap test?

After the first diagnosis of LSIL, a repeat Pap test should be performed in six months. If LSIL is seen again, 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 LSIL and to look for pre-cancerous and cancerous changes that can be seen with LSIL. Your doctor may also take a small sample of tissue from the endocervical canal and endometrium.

If the diagnosis of LSIL is confirmed, your doctor will discuss the treatment options with you.

There are several treatment options available:

  • Close follow-up with Pap tests and periodic colposcopies.
  • 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).

It is recommended that most patients diagnosed with LSIL undergo a repeat Pap test after 6 months. If you have been diagnosed with LSIL, talk to your doctor about the treatment options available for you.

by Jason Wasserman, MD PhD FRCPC, updated December 28, 2020
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