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Squamous Intraepithelial Lesion (SIL)

Squamous Intraepithelial Lesion (SIL) is the abnormal growth of squamous cells on the surface of the cervix.

The cervix is the lower part of the uterus. Both the uterus and the cervix are located in the pelvis and are close to the upper part of the vagina and the ovaries. In fact, the cervix connects the uterus and the vagina. The vagina leads to the outside of the body.

The surface of the cervix is made up of two different types of cells, squamous epithelial cells (the lining cells of the outer part of the cervix, or ectocervix) and columnar epithelial cells (the lining cells of the inner part of the cervix, or endocervix).

Early detection and treatment of precancerous cells can prevent them from becoming cancerous. Otherwise, the abnormal cells can become cancer and spread to other parts of the body.

If you have an abnormal Pap smear or have already been diagnosed with CIN, the Colposcopy Clinic provides treatment.

Pap tests can detect precancerous and cancerous conditions by collecting cells from the surface of the cervix. Sometimes these cells appear abnormal, or atypical, when looked at under a microscope, but they are not completely cancerous. These are called premalignant or precancerous cells, which means they might turn into cancer if not found and treated early enough. These precancerous lesions are commonly called cervical intraepithelial neoplasia (CIN).

These lesions have also been called squamous intraepithelial lesions (SIL) and there are two types:

Low-grade SIL - In this type of SIL, the changes are thought to be just starting. The changes can be in the size, shape, or number of cells that are on the surface of the cervix. In these low-grade lesions, the cells have only a few abnormal characteristics, but are still somewhat similar to the normal cells. Other common names for this low-grade SIL are mild dysplasia or cervical intraepithelial neoplasia type I (CIN 1).

High-grade SIL - In this type of SIL, the cells look very abnormal under the microscope. However, these cells are still only on the surface of the cervix. They are not invading the deepest parts of the cervix yet. These lesions are also called moderate or severe dysplasia, CIN II or III or carcinoma in situ (CIS).

The next step, in many cases, is a colposcopy (an exam with an instrument that visually magnifies the cervix) and removal of any areas likely to be precancerous or cancerous. Sometimes, the physician and patient may decide to repeat the Pap test later and proceed to colposcopy only if the second test shows more abnormal cells that might need removal.

Other treatments for this type of cervical cancer are:

• cone biopsy of the cervix, which is removal of a cone-shaped piece of the cervix with a surgical knife, laser, or wire loop
• hysterectomy, which is removal of the uterus.

Please note: Carcinoma in Situ is a term used for the early stage of cancer in which the tumor is confined to the organ where it first developed. The disease has not invaded other parts of the organ or spread to distant parts of the body. Most in situ carcinomas are highly curable. SIL can also be considered a carcinoma in Situ.

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See Also:

• LEEP/LLETZ--from the UMHS web site
  
  
• About HPV Vaccines--from the National Cancer Institute
  
  
• U-M experts weigh-in on HPV vaccine recommendations
• Cervical Cancer

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University of Michigan Comprehensive Cancer Center
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Ann Arbor, MI 48109

This site is part of the U-M Health System. The information presented is not a tool for self diagnosis or a substitute for professional care. © 2008 U-M Comprehensive Cancer Center