by Jason Wasserman MD PhD FRCPC
September 14, 2023
High grade squamous intraepithelial lesion (HSIL) is a precancerous condition that starts from cells on the outside surface of the cervix. If not treated it can lead to a type of cervical cancer called squamous cell carcinoma.
HSIL is a sexually transmitted disease caused by infection with human papillomavirus (HPV). The virus infects specialized squamous cells on the outside surface of the surface. Over time the infected cells develop genetic changes which lead to HSIL. There are many types of HPV but most cases of HSIL are caused by the high-risk types 16 and 18.
Yes. HSIL is considered a precancerous condition that can turn into a type of cervical cancer called squamous cell carcinoma over time. For this reason, most patients with HSIL are offered treatment to remove the area of abnormal tissue.
The diagnosis of HSIL is usually made after some cells are removed from the cervix 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. 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 HSIL are darker and larger than the squamous cells normally found in the cervix. 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 smear, the abnormal squamous cells often form small groups but individual abnormal cells may also be seen.
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 (IHC) 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. Cells that are producing large amounts of p16 will be called positive or reactive.
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. Talk to your doctor about the options available.
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 such as a LEEP, your pathologist will examine the margin closely to ensure there are no abnormal cells at the cut edge of the tissue. Pap smears and small biopsies do not have margins.
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. The number and type of margins described in your report will depend on the type of procedure performed to remove the tumour from your body.
Typical cervical margins include: