Most women who have a cervical screening test (smear) have a normal result, but out of 100 women who have cervical screening, about 6 will have abnormal cells in their sample. (NHS Cervical Screening leaflet, ‘Helping you decide’, May 2017)

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. When abnormal cells develop in the inner part of the cervix, this is called CGIN. The outside of the cervix (ectocervix) is lined by squamous cells. When abnormalities are diagnosed in the squamous cells, these abnormalities are known as CIN (see ‘What is CIN?‘).

CGIN stands for cervical glandular intra-epithelial neoplasia. It is an abnormality of the glandular tissue in the cervix. CGIN is usually classified as low grade (mild) or high grade (severe). High grade CGIN is the equivalent of CIN3.

CGIN can be multi-focal – this means that more than one area is affected at one time, with normal tissue lying between them. As it can be difficult to monitor and assess this type of abnormality further hospital based care is usually offered, often as an outpatient.

CGIN is not cancer but, if left untreated, these changes may develop into a type of cancer called adenocarcinoma (‘adeno’ means gland). A cervical screening test (smear) can also detect early cancer of the cervix, but very few women with an abnormal test result actually have cancer of the cervix.