Cervical abnormalities: CIN3 and CGIN

What is CIN?

Most women who have a cervical screening test have a normal result. However, about 7 - 10% of women tested have atypical or abnormal cells (Cervical Screening Programme England 2010-11). The screening report may describe the abnormal cells as dyskaryosis or dysplasia. This means that some cells of the cervix show changes that may need further investigation. Often such changes can be due to inflammation or infection.

The transformation zone is an area of the cervix where abnormal cells most commonly develop; they can be detected by cervical screening and colposcopy. Two different cervical cell types can become abnormal. The inside of the cervix (endocervix) is lined by glandular cells. The outside of the cervix (ectocervix) is lined by squamous cells. Squamous cell lesions can be seen in 90% of all cervical abnormalities. When diagnosed (after further tests), these abnormalities are known as a pre-cancerous condition called CIN. Abnormal cells can also develop in the inner part of the cervix (see ‘What is CGIN?’).

CIN stands for Cervical Intra-epithelial Neoplasia – which means abnormal cells found on the surface of the cervix.

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A cervical screening test (smear) can show that abnormal cells are present, but it can’t always show how deeply the abnormal cells go into the cervix. In order to diagnose and find the grade of the CIN, further tests may be needed on samples (biopsies) of the abnormal areas of the cervix. The biopsies are looked at under a microscope to find the grade of the CIN. This helps the doctor to decide on the most appropriate type of treatment.

CIN is divided into grades, which describe how far the abnormal cells have gone into the surface layer of the cervix. The cell changes can be classed as CIN1, 2 or 3. This classification is used to indicate how much of the cervix is affected by abnormal cells. The higher the number, the more of the cervix is affected and so treatment is given to remove the cells. CIN1 often goes back to normal without treatment but a repeat cervical screening test (smear) is needed to check that the cells have gone. Treatment is usually given to remove CIN2 or CIN3 abnormal cells (see ‘Treatments and their impacts).

CIN1 – indicates mild changes; affecting only one-third of the thickness of the surface layer of the cervix.

CIN2 – indicates moderate changes; affecting two-thirds of the thickness of the surface layer of the cervix.

CIN3 – indicates more severe changes (not cancer); affecting the full thickness of the surface layer of the cervix.

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CIN3 is not cancer of the cervix, but it is important to treat CIN3 as soon as possible. If left untreated, these abnormal cells sometimes go on to develop into cancer of the cervix. CIN3 may be referred to as severe dyskaryosis or severe dysplasia. Less commonly, it is called carcinoma-in-situ, though this term is rarely used these days.

CIN1, 2 and 3 rarely cause any symptoms, such as pain, discharge or bleeding. This is why women who do experience any or all of these symptoms should attend for cervical screening or see a doctor.

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Last reviewed April 2012.

Last updated April 2012.

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