Cervical cancer screening has been one of the most successful screening programmes with an estimated 2000 lives being saved due to the programme annually. It prevents around 70% of cervical cancers from developing. The programme involves women aged 25-64 years old.
Cervical cancer screening used to involve a pap smear that was assessed for dyskaryosis/dysplasia (synonymous terms) and the evidence of CIN (cervical intraepithelial neoplasia). The management was solely based on the degree of dysplasia, however, modern screening has allowed further risk-stratified management. The new NHS system is an HPV first system in which we test samples for high-risk strains of HPV (hrHPV). If it is hrHPV-positive, only then do we perform cytological examinations.
High risk strains include:
- HPV-16
- HPV-18
- HPV-31
- HPV-33
- HPV-45
- Grading for HPV is as such:
- CIN I - mild dysplasia. 1/3rd of thickness of epithelium covered in atypical cells.
- CIN II - moderate dysplasia. 2/3rds of thickness of epithelium is covered in atypical cells.
- CIN III - severe dysplasia. Full thickness of epithelium covered in epithelium. It is considered CIS at this stage and is still pre-malignant as it hasn’t Invaded through the basement membrane. The peak incidence of CIS is 25-29 years old.
Age | When you are invited |
24.5 years old | Up to 6 months before 25th birthday |
25 - 49 years old | 3-yearly |
50 - 64 years old | 5-yearly |
65> years old | Only if 1 out of 3 last tests were abnormal, or if you have not been screened since 50 years old. |
The test involves sampling cervical cells with a pap smear for the presence of HPV. If the cervix cannot be visualised for any reason, they should be referred to colposcopy. Cervical stenosis should also be referred to colposcopy.
If hrHPV is found, then liquid-based cytology is used to detect abnormal cell changes.
- hrHPV positive - if positive, we do a couple of things:
- Cytological sampling:
- Abnormal → colposcopy
- Normal → repeat test at 12 months.
- If repeat is hrHPV negative → continue normal recall.
- If repeat is hrHPV positive but cytology still normal → repeat test at 12 months once again.
- However, if still positive at 24 months → colposcopy.
- hrHPV negative - continue normal recall of screening programme. Unless on the:
- Test of cure pathway - people treated for CIN I, II, III need to be invited 6 months after treatment to see if cured.
- Untreated CIN I pathway
If the sample is inadequate, then a repeat is to be done within 3 months. However, if the sample is inadequate again, then colposcopy needs to be done.
What do we consider abnormal cytology?
- Borderline changes in squamous or endocervical cells
- Low-grade dyskaryosis
- High-grade dyskaryosis
- Invasive squamous cell carcinoma
- Glandular neoplasia
An inadequate sample is one that:
- Cannot fully visualise the cervix
- Contains insufficient cells
- Contains artefacts or obscuring elements such as lubricant, inflammation, blood, discharge.
- Incorrectly labelled.
Screening should be delayed if the lady is:
- Menstruating
- <12 weeks postpartum or termination of pregnancy or miscarriage
- Has vaginal discharge or pelvic infection
If samples are hrHPV positive and the cytology is abnormal then they are referred for colposcopy. At colposcopy, a colposcope is used to assess the cervix in great detail.
They look for abnormal changes that may indicate CIN or cancer. This is done through the use of acetic acid and iodine with a biopsy may be done to then confirm the diagnosis.
- Acetic acid - once applied to the cervix, abnormal areas turn white (acetowhite). This is because acetic acid coagulates proteins and in pre-cancerous/cancerous changes we get a lot more abnormal proteins present. You can think of acetic acid being like a hot frying pan, and just like an egg turns white due to coagulation of proteins when touching the hot frying pan, so are the abnormal proteins of the cervix coagulating when they meet with acetic acid.
- Iodine - normal tissue stains dark brown, however, CIN does not stain and turns a saffron-yellow colour. The endocervix does not stain either. The reason for this is that squamous cells contain glycogen, while columnar cells do not. Iodine is glycophilic and is taken up by the glycogen.
If any of these are positive, a biopsy is taken for a confirmatory histological diagnosis.
- Large loop excision of transformation zone (LLETZ) - most common treatment for CIN.
- Cone biopsy
- Cryotherapy
HPV is linked not only to cervical cancers, but also anal cancer, vulval cancers, vaginal cancers, and oral cancers. The HPV immunisation programme is aimed at protecting against the main oncogenic strains (HPV 16 and 18) as well as the strains that cause genital warts (6 & 11). It is known as the Gardasil 9 as it protects against 9 strains (6, 11, 16, 18, 31, 33, 45, 52 and 58).
- It is aimed primarily for both girls and boys aged 12-13 years old. If the vaccine was missed at the age of 12 or 13 then it is available to boys <18 years old and girls under <25 years old.
- It is also aimed at gay, bisexual and other men who have sex with men (GBMSM) patients under the age of 45 for protection against anal, throat and penile cancers.
Other people who may be offered the vaccine are:
- Transgender people who are felt to have the same risk as MSM patients.
- Sex workers
- HIV patients
The vaccine is now given as a single dose as of September, 2023.
HPV causes the development of koilocytes which are dyskaryotic.
Dyskaryotic cells may have the following abnormal features of the nucleus:
- Nuclear enlargement
- Irregular contours of the nuclear membrane
- Hyperchromasia of the nucleus (the nucleus stains darker than normal)
- Perinuclear halo
