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Smears and Management of CIN

colposcopy

The cervix has many unique features. It is the part of the uterus that protrudes at the top of the vagina and it often called "the neck of the womb". It has the function of retaining a baby during pregnancy until the onset of labour, when it progressively dilates to allow passage of the baby through the birth canal. In the non-pregnant state it has to allow flow of menstrual blood and other uterine secretions. It also produces mucous which prevents infection at the same time as facilitating the passage of sperm into the uterus, especially around the time of ovulation. These properties are mainly under the control of the female hormones.

The cervix has ligaments attached to it to support both the womb and the top of the vagina. The covering of the cervix is also unique in being partly like robust vaginal skin and partly like the more delicate, mucous secreting uterine cells. The point at which the two cell lines meet is called the transformation zone and is the area which is most prone to precancerous and cancerous change due to HPV infection.

Because of its position, the cervix can be brought easily into view during a vaginal speculum examination and cells can be obtained from it using a special spatula or brush. The cells were traditionally smeared onto a glass slide and inspected for abnormalities (also called the pap smear after George Nicholas Papanicolaou). Liquid based cytology is the current way of preserving the cells before their inspection. The aim of the smear programme is to detect pre-cancer

NHS screening commences at the age of 25 and, following a normal result, repeated every three years until the age of 50 when the interval increases to every 5 years until the age of 65 when routine recall ceases. Because of the natural history of the disease, a woman who has had negative smears up to this point is unlikely to develop cancer. There is also a progressive practical problem in obtaining good smears or carrying out adequate colposcopic examination as the crucial transformation zone, referred to above, retracts higher into the canal after the menopause.

When abnormal cells are identified, they are classified as inadequate, inflammatory, borderline or pre-cancerous. The pre-cancerous smears are further graded from CINI to III depending on their resemblance to normal cells or cancer, CIN being an acronym for Cervical Intraepithelial Neoplasm.

What does an abnormal smear mean?

1 in 20 smears are abnormal of which 1 in 2000 are cancerous. Depending on the degree of abnormality, the smear may need repeating after a period of time (usually six months) or you may be invited for . You may also require a colposcopy if you have symptoms such as irregular bleeding or discharge despite an apparently normal smear. It is most essential that every abnormal smear is followed up and properly managed.

digital colposcope
Digital Colposcope

Colposcopy

This simply involves inspecting the cervix with a magnifying microscope following application of a weak vinegar solution. A small biopsy may then be taken for microscopic analysis or, following a local anaesthetic injection, the entire abnormal area may be removed and sent for the same examination (LLETZ); this has the added advantage of providing simultaneous treatment. Alternatively, the examiner may decide to invite you for a smear or treatment at a later date.

Does the screening programme work?

The incidence of cervical cancer is falling but the activity in colposcopy clinics is increasing and significant numbers of women with cancer have failed to fully utilise the screening service which at best reaches 80% of the target population.

Further reading