Your pathology report for low grade squamous intraepithelial lesion (LSIL) of the cervix

by Jason Wasserman MD PhD FRCPC and Zuzanna Gorski MD FRCPC
September 1, 2025

Low grade squamous intraepithelial lesion (LSIL) is a precancerous condition of the cervix caused by infection with human papillomavirus (HPV). It is made up of squamous cells that have been infected and changed by the virus. These abnormal cells are usually found in the transformation zone, which is the part of the cervix where glandular cells are replaced by squamous cells.

In addition to the cervix, LSIL can also affect the vagina, vulva, anal canal, and peri-anal skin. Another name for LSIL in the cervix is cervical intraepithelial neoplasia 1 (CIN1).

Although LSIL is considered precancerous, it does not mean cancer is present. In most people, the immune system clears the infection and the cells return to normal. Only a small number of cases progress to a more advanced precancerous lesion or to cancer.

What is the risk of LSIL turning into cancer?

LSIL itself is not cancer, but it is associated with a small risk of developing into a type of cervical cancer called HPV associated squamous cell carcinoma if the abnormal cells are not cleared by the immune system. Most cases of LSIL resolve naturally, especially in younger people.

A related condition called high grade squamous intraepithelial lesion (HSIL) carries a much higher risk of turning into cancer compared to LSIL. Because of this difference, LSIL is usually monitored with regular testing, while HSIL usually requires treatment to remove the abnormal cells.

What are the symptoms of LSIL?

Most people with LSIL do not notice any symptoms. The condition is usually detected during a routine Pap test.

When symptoms do occur, they may include:

• Abnormal vaginal bleeding, especially after sex or between periods.

• Unusual vaginal discharge, which may be watery or contain blood.

• Pelvic pain or discomfort, although this is less common.

Because LSIL often does not cause symptoms, regular cervical screening is important for early detection and monitoring.

What causes LSIL?

LSIL is caused by infection with human papillomavirus (HPV). HPV is a very common virus that spreads through close contact, including sexual activity. Most HPV infections clear within a few years, but in some people, the infection persists and causes abnormal changes in squamous cells.

There are many different types of HPV. LSIL may be caused by both low-risk HPV types, such as HPV 6 and 11, and high-risk HPV types, such as HPV 16 and 18. Low-risk HPV infections rarely lead to cancer, while high-risk HPV types are more strongly linked to progression.

Factors that increase the risk of LSIL include:

• Persistent HPV infection.

• A weakened immune system.

• Cigarette smoking, which makes cervical cells more vulnerable to HPV-related changes.

• Long-term use of birth control pills.

• Multiple sexual partners, which increases the chance of exposure to HPV.

• Lack of regular cervical screening.

How is the diagnosis of LSIL made?

LSIL is usually detected first on a Pap test. A Pap test collects cells from the surface of the cervix and allows a pathologist to look for changes caused by HPV infection.

If LSIL is reported on a Pap test, additional tests may be performed:

• HPV testing checks for the presence of high-risk or low-risk HPV types.

• Colposcopy is an examination of the cervix using a special magnifying device.

• Cervical biopsy removes a small sample of tissue from any suspicious area to confirm the diagnosis and rule out HSIL or cancer.

• Endocervical curettage collects cells from inside the cervical canal that may not be visible during colposcopy.

If the biopsy confirms LSIL, most patients are managed with monitoring and follow-up testing rather than immediate treatment.

What does LSIL look like under the microscope?

When examined under the microscope, LSIL shows squamous cells that look different from normal cells. The cells are larger and darker, and the material inside the nucleus, called chromatin, often looks irregular or clumped.

Some cells have two nuclei instead of one, which is a common feature of HPV infection. Other cells show clear areas around the nucleus, creating a halo-like appearance. These are called koilocytes and are considered a hallmark of HPV-related changes.

Special tests such as immunohistochemistry for p16 may be performed. Unlike HSIL, LSIL cells are usually negative or only weakly positive for p16.

What is the treatment for LSIL?

Most cases of LSIL do not require immediate treatment because the condition often resolves on its own, particularly in young women. Instead, doctors usually recommend regular follow-up to monitor the cervix and ensure the abnormal cells do not progress to HSIL or cancer.

Common management options include:

• Repeat Pap tests every 6 to 12 months.

• HPV testing to check for high-risk HPV types.

• Colposcopy and biopsy if LSIL persists or if high-risk HPV is present.

• In some cases, procedures such as cryotherapy or laser therapy may be used if LSIL persists for a long time.

What should happen after LSIL is diagnosed on a Pap test?

If LSIL is found on a Pap test, your doctor will decide on a follow-up plan based on your age, HPV test results, and biopsy findings.

• If LSIL is confirmed but high-risk HPV is not present, repeat testing in several months may be all that is required.

• If LSIL is confirmed and high-risk HPV is present, colposcopy and biopsy may be recommended.

• If LSIL progresses to HSIL, treatment to remove the abnormal cells will be required.

Because LSIL has a low risk of progression, surgery is usually not necessary unless the lesion persists or worsens over time.

What are margins and why are they important?

Margins are the edges of tissue removed during a surgical procedure. Margins are not usually assessed in LSIL because most people do not need surgery. However, if LSIL is treated with procedures such as LEEP, cone biopsy, or laser therapy, the pathologist will check the margins under the microscope.

• A negative margin means no abnormal cells are seen at the edge, suggesting the lesion was fully removed.

• A positive margin means abnormal cells are present at the edge, which increases the chance of recurrence.

Margins are only reported for tissue removed during surgery, not for Pap smears or small biopsies.

Questions to ask your doctor

• Was LSIL the only finding on my Pap test or biopsy?

• Did my sample test positive for high-risk HPV?

• What type of follow-up plan do you recommend for me?

• How often will I need Pap tests or HPV testing?

• At what point would treatment be needed instead of monitoring?

• Does my smoking status, immune health, or medical history affect my risk of progression?