by Jason Wasserman MD PhD FRCPC
March 22, 2022
Low-grade squamous intraepithelial lesion (LSIL) is a non-cancerous, sexually transmitted disease caused by infection with a virus called the human papillomavirus (HPV). This condition may affect both women and men. In addition to the cervix, LSIL can also affect the vagina and vulva. In both women and men, LSIL may also involve the anal canal and peri-anal skin.
LSIL develops after the specialized squamous cells on the surface of the cervix become infected by the virus. Infected cells show an abnormal pattern of development called dysplasia. 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 tissue will return to normal. High-grade squamous intraepithelial lesion (HSIL) is a related condition that is also caused by HPV. However, compared to LSIL, the risk of developing cancer from HSIL is much higher.
The diagnosis of LSIL is usually made after some cells are removed from the cervix in a procedure called a Pap test or a biopsy. The diagnosis can also be made when part or all of the cervix is removed for another reason. The tissue sample is then sent to a pathologist who examines it under the microscope.
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.
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.
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.