Squamous intraepithelial lesion


A squamous intraepithelial lesion (commonly abbreviated SIL) is a general term for the abnormal growth of squamous cells on the surface of the cervix. Squamous cells are flat, scale-like types of epithelial cells. Epithelial cells are cells that help absorb, move, and distribute some of the fluids and nutrients in the body. The cervix is a small, cylinder-shaped organ that forms the lower part and neck of the uterus. The uterus is a hollow organ in a female's body where the egg is implanted and the baby develops.


The terms "low grade" and "high grade" (in reference to squamous intraepithelial lesions) refers to how abnormal the cells are and how much of the cervix is affected. A low grade squamous intraepithelial lesion (commonly abbreviated LGSIL) is one in which the cells are not very abnormal and not much of the cervix is affected. A high grade squamous intraepithelial lesion (commonly abbreviated HGSIL) is one in which the cells are very abnormal and much of the cervix is affected.
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Squamous intraepithelial lesions are usually diagnosed with a Pap smear or colposcopy. A Pap smear is a type of test used to detect abnormal changes in cells. This is done by scraping away loose cells from the cervix, spreading (smearing) it on a glass slide, and examining it under a microscope. A colposcopy is a visual examination of the vagina and cervix with a lighted magnifying instrument, known as a colposcope. The vagina is an opening in the female's body that is part of the reproductive system.

The definitive way to diagnose a squamous intraepithelial lesion is with a biopsy done during a colposcopy. A biopsy is the process of removing living tissue or cells from organs or other body parts of patients for examination under a microscope or in a culture to help make a diagnosis, follow the course of a disease, or estimate a prognosis. A culture is an artificial way to grow cells or tissues in the laboratory.

The above procedures are usually performed by an OB/GYN, which stands for obstetrician and gynecologist. An obstetrician is a physician (medical doctor) who specializes in obstetrics, which is the science that deals with the care of women and their fetuses during pregnancy and childbirth, and during the events that come before and soon after birth. A gynceologist is a physician who specializes in gynecology, which is the science that deals with the health care of women, including diseases and normal physical care of the female reproductive system.


Having a squamous intraepithelial lesion does not mean that cancer is present. Cancer is an abnormal growth of new tissue characterized by uncontrolled growth of abnormally structured cells that have a more primitive form. The presence of squamous intraepithelial lesions represents changes in cells that can occur before cancer is present. Thus, squamous intraepithelial lesions are often seen by doctors as warnings that cancer of the cervix may occur at a later date.

It should be noted that the chances of having a high grade intraepithelial lesion showing up on a Pap smear with invasive cancer of the cervix already being present is less than 1%. Also, only about 1.5% of women with a high grade intraepithelial lesion that shows up on a Pap smear will progress to cancer of the cervix within the next 24 months.


Since squamous intraepithelial lesions can progress to cancer of the cervix, it is important for them to be treated. The results of the colposcopy, and not the Pap smear, will provide the basis for treatment. This is because a colposcopy (combined with a biopsy) is a more definitive test than the Pap smear.
The goal of treatment is to destroy and/or remove the abnormal cells on the cervix so that new healthy cells will grow over the area where the abnormalities were present. Squamous intraepithelial lesions can be destroyed by applying below-freezing temperatures to them, by using lasers, or by applying heat and/or electrical currents. If abnormal areas of tissue need to be totally removed, a colposcopy is often used as a visual aid during surgery. Removal of the tissue can take place during the biopsy or at a later time if the patient desires.

It is important to note that if there is disease inside the canal (passageway) of the cervix, doctors do not freeze the disease tissue. Freezing is generally used in small areas of abnormality (even if they are severe) that do not enter the canal of the cervix. Freezing tissue usually only takes a few minutes to do in the doctor's office. Healing from this freezing procedure will take about 3 weeks. A watery liquid will usually come out of the vagina during the healing process after the freezing procedure.
Destroying tissue with laser or heated electrical current is usually more appropriate for larger areas of abnormality. Presently, this is the most frequently used treatment for high grade intraepithelial lesions. Larger abnormal areas (even if they are mildly abnormal) are more than an inch wide, more than a half inch from the bone by the cervix, or in more than two quadrants of the cervix. A quadrant is a division into four areas. Abnormal areas that enter the canal of the cervix generally respond best to treatment with laser therapy or electrical current.

The abnormal cells that are removed are usually located at the transformation zone of the cervix. The transformation zone is located in the outside of the cervix or in the canal of the cervix. The transformation zone is the area where tall cells shaped like a column (known as columnar cells) are transformed (changed) into flat cells known as squamous cells. It is in the transformation zone that abnormalities develop. In general, any procedure that destroys squamous intraepithelial lesions on the cervix cures the condition in about 85% of the cases.


Squamous intraepithelial lesion comes from the Latin word "squama" meaning "scale," the Latin word "intra" meaning "within," the Greek word "epi" meaning "upon," the Greek word "thele" meaning "nipple," and the Latin word "laesus" meaning "an injury." Put the words together and you have "scale within upon nipple an injury."