Family doctor

Overview:

• Cervical screening aims to identify abnormal cells which can lead to cancer
• A cervical smear removes cells from the surface of the cervix for examination under a microscope.
• Patients with abnormal smears will need a colposcopy to diagnose the cause
• About seven percent of smears show abnormal cells
• An abnormal smear rarely means cancer
• Low-grade pre-cancerous changes may resolve without treatment
• High-grade cancerous changes usually require prompt treatment
• 95 percent of women are cured after one treatment

What is cervical screening?

The purpose of cervical smears screening is to identify abnormal cells while they are still confined to the skin layer on the cervix. This is the pre-cancerous state, also called cervical intraepithelial neoplasia (CIN).

Cervical cancer generally has a well-defined progression from this detectable CIN stage. It usually takes 10 - 15 years before the abnormal pre-cancerous cells breach through the base of the skin and become capable of invading other parts of the body (invasive cancer). Treatment at the stage of CIN should prevent cancer developing.

It must be remembered that cervical smears are samples of loose cells from the surface of the cervical skin. The cervical smear does not always accurately reflect what is occurring in the whole of the skin layer - and it is the latter which is important to make the diagnosis of CIN. In order to obtain full thickness skin specimens from the cervix, for histological examination, patients with abnormal smears require colposcopy and skin biopsies.

Colposcopy enables a detailed examination of the cervical skin with a lighted microscope, and any abnormal looking areas of skin can be sampled (biopsied) to give a more accurate assessment of the true degree of CIN.

Pre-cancerous cells can develop in two different cell types of the cervix.

1. The outer part of the cervix has squamous cells and these make up 90% of the abnormalities. These pre-cancerous cells are CIN.

2. The inner part of the cervix within the cervical canal has different glandular cells. Pre-cancerous changes are called adenocarcinoma - in - situ (AIS) and make up 10% of abnormal cells.

Only 7% of cervical smears show atypical or abnormal cells. An abnormal cervical smear rarely signifies cancer

These are four general categories of abnormal smears-

1. Atypical cells of undetermined significance (ASCUS)

The cells (either squamous or glandular) show changes beyond normal, but not enough to definitely be called abnormal. Usually a repeat smear in 6 months is recommended and many will revert to normal and not require any further investigation. If however a second smear is the same, then more detailed examination by colposcopy is warranted. For women with persistent atypical cells on smears, a significant proportion will have truly pre-cancerous changes (CIN).

2. Abnormal cervical smears

Low grade changes (of squamous cells). The cell changes on the smear are only mildly abnormal and these may be due to mild pre-cancerous skin on the cervix (CIN1); or to cell changes from human papilloma virus infection (HPV). This virus also used to be called the "wart virus" though most women with this virus do NOT have visible warts.

HPV is a very common contagious viral infection in sexually active people and there are 40 different varieties. Many will result in mildly abnormal cells on the smears which are similar to those of CIN1. A few of the HPV types are linked with an increased risk of true invasive cancers.

Women with low-grade changes and no previous abnormalities, should have their next smears repeated in 6 months. If this next smear is abnormal, then colposcopy is recommended.

Women with smears suggesting HPV alone, are managed in the same way as those with smears suggesting CIN1.

Over half of the low grade abnormalities will disappear if watched closely by six monthly smears and colposcopy. If the low-grade changes remain or deteriorate, then treatment is indicated. The 1998 New Zealand National Cervical Screening Programme recommendation for long term follow-up of proven low grade changes (CIN1 and/or HPV) is no longer annual smears for life. The new recommendation is a return to 3-yearly screening provided there have been three normal smears after diagnosis and spontaneous cure or successful treatment.

3. High grade changes (of squamous cells)

These smears suggest abnormal cells originating from moderate (CIN2) or severe (CIN3) pre-cancerous skin on the cervix.

All women with these smears should be seen within one month for colposcopy. If the abnormality is proven by biopsy, then treatment is recommended. Long term follow-up after treatment of CIN 2-3 is annual smears until age 70 years.

4. High grade changes (of glandular cells)

Adenocarcinoma-in-situ (AIS) is not as common as squamous abnormalities (CIN). It requires prompt referral for colposcopy and most often requires treatment. Long term follow-up is annual smears.

Treatment of CIN

Treatment is to remove the abnormal area of skin. 95% of women will be cured with one treatment, but 5% may have further abnormalities and need another further treatment.

There are a variety of treatments and the one chosen will depend on the gynaecologists preference, the equipment available and what sort of abnormality there is.

LLETZ treatment (Large Loop Excision of the Transformation Zone)

A thin wire loop with electrical current is used to scoop off strips of tissue from the cervix. The tissue is sent for laboratory examination.

Laser treatment

A laser beam is used to vaporise and destroy (ablate) the abnormal area, or the laser can be used to cut out a core of tissue (cone biopsy) for examination.

Cryosurgery

Intense cold from a probe is used to destroy the tissue.

Surgical cone biopsy

A scalpel can be used to cut a core or cone biopsy from the cervix and this tissue can be examined.

Hysterectomy

Sometimes if the above simpler measures are not appropriate, or the woman has additional gynaecological problems, then a hysterectomy may be more appropriate as it will remove both the cervix and uterus in total. This surgery requires a general anaesthetic.

Risks of treatment

There are small risks with all surgery but most localised treatments to the cervix are well tolerated. Many women can cope with local anaesthetic injections to the cervix, but some may wish to have intravenous sedation or even general anaesthetic.

Bleeding (at the time of surgery, or in the 2 - 3 weeks afterwards) or infection (more often in the two weeks after) are uncommon but recognised complications.

Generally, a single, straightforward localised treatment to the cervix is very unlikely to adversely affect a woman's fertility or her ability to have a normal pregnancy.

Follow-up treatment

A colposcopy and smear are performed 4 - 6 months after treatment by the gynaecologist and then annual smears by her general practitioner or smear taker. The length and frequency of long term follow-up is discussed earlier in this article.