Squamous intraepithelial lesion (SIL)

Squamous intraepithelial lesion is an abnormal growth caused by infection with human papillomavirus (HPV). This condition affects the squamous cells, which are thin, flat cells that line certain areas of the body, including the cervix, vagina, vulva, and anus. Squamous intraepithelial lesion is considered a precancerous disease, meaning it has the potential to develop into cancer. However, the risk of developing cancer depends on the grade of the lesion, with high grade lesions carrying a higher risk than low grade lesions.

What are the symptoms of squamous intraepithelial lesion?

Most people with a squamous intraepithelial lesion do not have any symptoms, which is why the condition is often detected during routine screening tests, such as a Pap test for cervical cancer. In some cases, there may be mild symptoms, such as abnormal bleeding or discharge, depending on where the lesion is located.

What causes squamous intraepithelial lesion?

Squamous intraepithelial lesion is always caused by infection with the human papillomavirus (HPV). HPV is a common virus spread through direct contact, including sexual contact. Certain types of HPV are more likely to cause the abnormal cell changes seen in squamous intraepithelial lesions.

Low grade versus high grade squamous intraepithelial lesion

Pathologists divide squamous intraepithelial lesions into two categories: low grade and high grade. Low grade squamous intraepithelial lesion (LSIL) indicates mild changes in the squamous cells that are often temporary and may resolve on their own without treatment. High grade squamous intraepithelial lesion (HSIL) involves more severe changes, which carry a higher risk of progressing to cancer if left untreated. The categorization of squamous intraepithelial lesion helps doctors decide on the best approach for monitoring or treating the lesion.

How is this diagnosis made?

The diagnosis of a squamous intraepithelial lesion is made after examining cells from the affected area under a microscope. Cervical lesions often involve a Pap test or a biopsy (a small tissue sample). A pathologist examines these cells to identify any abnormal changes.

What are the microscopic features of squamous intraepithelial lesion?

Under the microscope, squamous intraepithelial lesions show specific changes in the squamous cells’ shape, size, and arrangement. Pathologists examine these changes to determine whether the lesion is low grade or high grade. These microscopic details are essential for understanding the lesion’s severity and guiding treatment decisions.

What is p16 and how does it aid in the diagnosis?

p16 is a protein that helps control cell growth. Strong p16 expression supports the diagnosis of a high grade squamous intraepithelial lesion. Testing for p16 by immunohistochemistry (IHC) allows pathologists to confirm the diagnosis, especially in cases where the cell changes are more severe and may have a higher risk of progressing to cancer.