A squamous intraepithelial lesion (SIL) is an area of abnormal tissue on the skin inside of your body. It can affect the cervix, vagina, vulva, anus, penis or back of the throat. These lesions are precancers, which means they’re not cancer but have the potential to become cancer and spread to other tissues.
A squamous intraepithelial lesion (SIL) is an area or spot of skin on the inside or outside of your body that grows in a more disorganized way than the skin around it. These areas of skin can form on the lining of certain body parts, like your cervix, vagina, vulva, anus, penis and the back of your throat.
Skin that develops lesions found to be an SIL is usually the result of a virus called the human papillomavirus, or HPV. The skin changes (SIL) themselves cannot be spread from person to person, but the virus can be transmitted through sex as a sexually transmitted infection (STI).
Usually, SILs can be considered “precancers.” This means they aren’t cancer, but they could become cancer if the abnormal cells grow into deeper layers of tissue. SILs can also be called “dysplasia” or “neoplasia”.
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Healthcare providers classify SILs as low-grade or high-grade:
You’re at an increased risk for SIL if you:
Squamous intraepithelial lesions are common. For instance, healthcare providers diagnose around 200,000 women with cervical dysplasia (SIL) each year. Approximately, 14,000 women will develop cervical cancer due to HPV.
The most common HPV-related cancer in men is oropharyngeal cancer, which is in the back of the throat. It affects about 11,800 men each year.
An HPV vaccine can prevent up to 90% of HPV-related SILs and cancers.
Human papilloma virus (HPV) is a sexually transmitted infection (STI) that causes SIL. There are over 100 different types of HPV infections, but dysplasia that can lead to cancer is usually the result of types 6, 11, 16 and 18. Newer high-risk strains are types 31, 33, 45, 52 and 58.
Repeated HPV infections or infections that last in your body for a long time cause damage to cells. In some people, the cells turn cancerous.
An SIL doesn’t usually cause symptoms. Most people find out they have it after an exam at their doctor’s office.
Let your healthcare provider know right away if you notice any of the following symptoms in your genitals:
Precancer in the back of your throat may cause:
There are a variety of tests that can screen for and diagnose SILs:
It’s important to note that SIL and cancer can take many years after an HPV infection to develop.
Out of all the HPV-related cancers, routine screening is only recommended for cervical cancer. The U.S. Preventive Services Task Force recommends routine cervical cancer screening for women aged 21 to 65. Based on your age, screening may include a Pap smear, an HPV test or both.
Talk to your healthcare provider about the right screening guidelines for your age and risk level. You may need more frequent screenings if you’ve tested positive for HPV or had abnormal Pap smears in the past.
Most low-grade lesions go away on their own. High-grade lesions require immediate treatment. Depending on the location of the lesions, your healthcare provider may recommend:
The best way to prevent squamous intraepithelial lesions is by getting the HPV vaccine. Girls and boys ages 9 to 14 can get the HPV vaccine series, which is two or three shots spaced two to 12 months apart. If you get the vaccine when you’re older, between ages 15 and 45, you’ll need three doses. If you’re older than 46, talk to your healthcare provider before getting the HPV vaccine.
Other ways to reduce your risk of HPV include:
Mild (low-grade) SIL usually goes away on its own. Moderate to severe (high-grade) SIL that’s treated early usually doesn’t turn into invasive cancer.
Questions you might want to ask your healthcare provider include:
Contact your healthcare provider if you notice any abnormal symptoms in your genitals, mouth or throat. You should also talk to your healthcare provider if you think you may have had genital contact with someone who has HPV.
A note from Cleveland Clinic
Squamous intraepithelial lesions (SILs) are areas of abnormal tissue that may become cancerous. They’re usually the result of HPV but might not develop until long after you get the infection. SILs typically affect your cervix, vagina, vulva, anus, penis or back of your throat. Some SILs go away on their own, but others need immediate treatment to remove the abnormal tissue before cancer develops.
Last reviewed by a Cleveland Clinic medical professional on 10/26/2021.
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