Cervical cancer screening

Notes

Introduction

NHS Cervical Screening Programme (NHSCSP) that screens women and transgender men (with retained cervix) aged 24.5-64.

At 24.5 women are invited, with the aim for the first screen to be completed before the age of 25. Under normal conditions women, transgender men (with retained cervix) and non-binary individuals (assigned female at birth) are invited every 3 years between ages 25-49 and every 5 years between 50-64 years.

Those aged 65 or older may have screening if they have not had one since 50 and request it or have had a recent abnormal screen. Transgender men with a retained cervix should be invited for screening unless they have opted out. Of note, if they are registered with their GP as a man they will not receive automated referrals and need to request appointments.

Screening

Screening involves a cervical smear.

The cervix should be visualised with a speculum (abnormal macroscopic appearances should be urgently referred to gynaecology on a cancer pathway). The cytology sample is taken from the transformation zone. Analysis is in two steps:

  • Primary hrHPV screening: Cervical cells from a smear test are reviewed for the presence of high risk HPV. If they are present, cytology will be completed. 
  • Liquid based cytology: If hrHPV found on screening then cytology of cervical cells will be completed. Cytology may be normal, abnormal or inadequate. Abnormal cells trigger a referral for colposcopy.

Reasons for delay

Cervical screening may be temporarily delayed in a number of circumstances.

If it is unlikely the patient will return, a decision will have to be made about taking the sample whilst acknowledging the context. Reasons to delay include:

  • Women is menstruating
  • Abnormal vaginal discharge / pelvic infection
  • Less than 12 weeks postnatal
  • Less 12 weeks after a termination of pregnancy or miscarriage

Pregnancy

In pregnant women normally a routine screen will often be rescheduled to 3 months post-partum. 

If a women has had an abnormal screen and subsequently falls pregnant, management should be guided by specialists.

Immunocompromised 

Under certain circumstances additional screening may be indicated.

In appropriate patients aged 25-64, offer additional screening if:

  • Renal failure requiring dialysis (or any other disease with a high chance of needing organ transplantation): Screen at time of diagnosis
  • If planned to have organ transplantation: Screen within a year before transplantation.
  • HIV: Screening at diagnosis, then yearly screen advised.

Additional screening guidelines may exist for patients with various conditions or taking immunosuppressants. This tend to follow local guidelines and are managed by specialists.

There are numerous unique cases. Daughters of women exposed to diethylstilbestrol (DES) may undergo more frequent screening or colposcopy.

Referral for colposcopy

Those with abnormal cytology or repeated inadequate cytology or hrHPV positive samples are referred for colposcopy.

Colposcopy allows optimal and magnified visualisation of the cervix and for biopsies to be taken. Around 40% of colposcopies will be normal.

Abnormal cytology

Those with borderline change in squamous, endocervical cells, low-grade dyskaryosis are referred for colposcopy, with an appointment expected within 6 weeks

Those with high-grade dyskaryosis (moderate or severe), suspected invasive cancer or glandular neoplasia will be referred to colposcopy within 2 weeks.  

Inadequate cytology

Inadequate samples should be repeated within 3 months. If two are inadequate the patients are referred for colposcopy. The same is true if hrHPV tests are unavailable recurrently. 

hrHPV positive, cytology negative

Patients who are hrHPV positive with normal cytology, repeat screening is recommended at 12 months. If negative they may return to the normal screening programme. 

If still hrHPV positive at 12 months (and cytology negative), repeat again at 12 months (i.e. 24 months after initial smear). If positive again refer for colposcopy.

CIN

Cervical intraepithelial neoplasia (CIN) refers to pre-malignant cervical dysplasia.

CIN are premalignant epithelial lesions that may progress to cancer.

  • CIN 1: Mild dysplasia, malignant progression unlikely, most self resolve.
  • CIN 2: Moderate dysplasia, higher risk of progression to malignancy.
  • CIN 3: Severe dysplasia, highest risk of progression to malignancy. 

Figures vary from study to study but CIN 3 is associated with around an 18% risk of progressing to invasive cancer over 10 years.

Patients with CIN 1 will typically be brought back for repeat review at 12 months. CIN 2 may resolve but risk of cancer is increased and removal is typically indicated. In CIN 3 removal is always advised.

Surgical management options include knife cone biopsy, laser conisation, large loop excision of the transformation zone (LLETZ), l and cryocautery amongst others.

Further reading

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