Cervical intraepithelial neoplasia (CIN)

The main cause of CIN is an infection called the human papilloma virus (HPV). There are over 100 types of this virus. Some types of HPV can affect the cervix. The types that cause abnormal cell changes in the cervix are called high-risk HPV

Usually, the body’s immune system gets rid of the infection naturally. There are no symptoms and often the virus does not cause damage. Most people will never know they had it.

In some people, the immune system does not get rid of the infection and the virus stays in the body for longer. We do not know exactly why this is. If the cervix is affected by HPV for a long time, the virus can cause damage that may eventually develop into CIN.

HPV is very common, and most people are infected with it at some point. It can affect all sexual orientations and anyone who has ever been sexually active. This includes people in a long-term relationship with one partner. HPV may still affect you even if you have not been sexually active for some years. 

The virus can live on the skin around the whole genital area. It passes easily from person to person during any type of sexual contact, including skin-to-skin genital contact or sharing sex toys. Using a condom or other barrier contraception may reduce your risk of HPV infection, but it does not offer complete protection.

Your risk of developing CIN is higher if you smoke. This may be because:

• smoking makes your immune system less effective at getting rid of HPV
• the chemicals in tobacco can damage your cells.

If you want to stop smoking:

• in England, contact NHS Smokefree
• in Scotland, contact Stop Smoking
• in Wales, contact Help Me Quit
• in Northern Ireland, contact Stop Smoking.

The first part of cervical screening is a smear test. This does not show if you have CIN. But if your test result shows abnormal cells, you may then have a test called a colposcopy.

The colposcopy shows abnormal areas of the cervix and how abnormal the cells are. It can be used to diagnose CIN and to decide if you need treatment.

CIN 1 means one-third of the thickness of the cervical surface layer is affected by abnormal cells. This will often return to normal without any treatment at all. You will have further cervical smear tests or colposcopies to check the cells have improved. If these tests show the CIN 1 is not improving, you may be offered treatment.

CIN 2 means two-thirds of the thickness of the cervical surface layer is affected by abnormal cells. There is a higher risk the abnormal cells will develop into cervical cancer. You may be offered treatment to stop this happening, or another colposcopy.

CIN 3 means the full thickness of the cervical surface layer is affected by abnormal cells. CIN 3 is also called carcinoma-in-situ. This sounds like cancer, but CIN 3 is not cervical cancer. Cancer develops when the deeper layers of the cervix are affected by abnormal cells. You will be offered treatment to stop this happening.

Treatments for CIN are usually very successful. To check, you will be asked to have another cervical smear test about 6 months after your treatment. Your sample will be carefully checked for signs of abnormal cells and for high-risk HPV. What happens next depends on the results:

• If the sample shows no HPV
  You will be asked to have cervical screening again in 3 years. Your risk of developing more serious abnormal changes in this time is very low.
• If the sample shows HPV
  You will be asked to have another more detailed check-up, with a colposcopy.

Sometimes the colposcopy shows that an abnormal area of cells has come back and more treatment is needed. This does not happen often. The same types of treatment can often be used again to remove or destroy the abnormal area of cells.

Very occasionally, if the abnormal cells keep coming back after treatment, your doctor might suggest having surgery to remove the cervix completely. This usually means having an operation called a hysterectomy. Your doctor will explain if they think this is right for you.

After a hysterectomy, you may still need tests to check for abnormal cells. This is similar to having a cervical smear test, but the sample of cells is taken from the top of the vagina. It is sometimes called a vaginal vault smear.

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• use plain English
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