Pap test results

Low grade squamous intraepithelial lesion (LSIL)

by Adnan Karavelic, MD FRCPC, updated on August 28, 2019

Quick facts:

  • Low grade squamous intraepithelial lesion (LSIL) is a non-cancerous condition that develops in the cervix.
  • LSIL is caused by a virus called human papillomavirus (HPV) which infects cells on the surface of the cervix.
  • LSIL can turn into a cancer over time although the risk is very low.

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 low grade squamous intraepithelial lesion (LSIL)?

Low grade squamous intraepithelial lesion (LSIL) is a non-cancerous disease that develops from the squamous cells in the cervix. 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 cervix will return to normal.

Why is this important? Patients diagnosed with LSIL should be offered a repeat Pap test in 6 months to see if the condition has resolved.

How do pathologists make this diagnosis?

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. While normal squamous cells have one nucleus, some of the abnormal cells in LSIL may have two nuclei. The abnormal cells in LSIL are usually in small groups or as single cells. Some normal squamous cells may also be seen at the same time. The abnormal cells found in LSIL are sometimes called koilocytes.

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).

Why is this important? 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.

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