Cervical Screening and Abnormalities
A historical summary of cervical (Pap) smear tests
In 1928 Dr Papanicolaou discovered that cells from the cervix change in microscopic appearance before they become cancerous. These precancerous changes form the basis of identification and interpretation of precancerous cells and the cervical smear is most commonly know as the Pap smear.
There is a common misconception that the Pap smear is used to identify cervical cancer. In fact, Pap smears are not very good at identifying cervical cells that have already undergone cancerous (malignant) change. They are much more effective at picking up the changes in cervical cells, that if left untreated, might progress to cancer.
The frequency of routine Pap smears is dictated by the protocol of the Country in which you live in. In Australia, routine Pap smears are performed every 2 years and in the UK every 3 years. A balance is made by the authorities between the costs (financial to population and emotional/inconvenience to patients) of screening and the comparative prevention of cervical cancer with increased screening frequency.
- Every year around 800 Australian women are diagnosed with cervical cancer.
- Most cervical cancer is preventable with regular screening.
- The majority of women diagnosed with cervical cancer are either under-screened or have never been screened.
The Cervical Screening Test (Australia, 1.12.17)
- A 5-yearly Cervical Screening Test will replace the 2-yearly Pap test.
- Patients who have ever been sexually active should commence screening at 25 years of age and have a CST every 5 years until they reach 74 years.
- Patients who have been vaccinated against HPV still need to be screened.
- Healthcare providers will still perform a vaginal speculum examination and take a cervical sample.
- The sample medium is liquid-based and will be tested for the presence of HPV
- The new National Cancer Screening Register (NCSR) supports the new Cervical Screening Test.
- The NCSR sends invitations/reminder letters to patients when they are due, and follow-up letters when patients have not attended further investigations or tests.
- 80% of Australian patients who develop cervical cancer are under-screened or have never-screened.
- The CST and pathway is a risk-based approach where patients are managed according to their risk of developing significant cervical abnormalities.
- There are 3 risk categories: low risk, intermediate risk and higher risk.
Obtaining a Cervical Screening Test Sample
A speculum is introduced into the vagina. A bi-valve speculum is most commonly used but other speculums may be used. The cervix is brought in to view by opening up the speculum
A thin cytobrush is used to obtain an endocervical sample by introducing it into the endocervical canal and twisting the brush around.
A broader cytobrush is used to obtain a wider endocervical and ectocervical sample by introducing the forward tip into the endocervical canal and twisting the brush around. The outer parts of the brush pick up cells from the ectocervical area.
New technology allows material from the cytobrush to be placed in a special liquid in a bottle (labelled so as to identify the patient). The fluid can be spun down in the lab to isolate cells from the cervix. This is important if the material on the slide is obscured by blood.
Whilst obtaining a sample of cervical cells, it is important to be able to visualise all of the cervix. This is important because screening tests are not very good at identifying cervical cancer, but a visual examination will likely identify a potentially malignant lesion that needs biopsy for diagnosis, even if the CST is normal.
The prepared slides are examined under a microscope by specially trained pathologist called cytologists. In Australia, the slide will be examined by two cytologists and a report produced that will reflect an agreed position on the normality or otherwise of the specimen.
Pap smear reporting
- No abnormal changes noted in the cells obtained from the cervix.
- Ideally, the sample would have contained both endocervical and ectocervical cells.
- In some cases, the report will indicate that though the cells sampled show no abnormality, there are no endocervical cells identified.
- Routine followup can occur if there are no endocervical smears as long as there is no history of cervical abnormality, the Pap smear has been reported as normal and the cervix looks visually normal.
- Atypia and non-specific minor changes
- Minor changes (‘atypia’).
- Caused by HPV, various bacterial, fungal or viral infections.
- Usually repeat Pap smear in 6-12 months and refer for colposcopy if persists.
- Cervical intraepithelial neoplasia-1 (CIN-1)
- Minor changes in size and shape of cervical cells.
- 6/10 will heal without intervention.
- 4/10 remain unchanged or progress to CIN-2 or CIN-3.
- Repeat Pap smear in 4-6 months and refer for colposcopy if persists.
CIN-2 and CIN-3
- CIN-2 also known as moderate dysplasia
- CIN-3 also known as severe dysplasia.
- More often considered as precancerous changes.
- If left untreated may progress, usually over several years, to cervical cancer.
- Referral for colposcopy + cervical biopsy will be made.
- More likely to require treatment.
Progression of change
Low Grade Squamous Intra-epithelial Lesion
High Grade Squamous Intra-epithelial Lesion
All abnormal, precancerous cervical changes have the potential to regress to normal. This is most likely to happen with LSIL (low grade changes) and less likely to happen with HSIL (high grade changes). Atypical changes may regress spontaneously or after appropriate treatment with antibacterial or anti fungal therapy if indicated. There is no spontaneous regression of cancer, whether micro-invasive or invasive.
Human Papilloma virus (HPV)
HPV is found in approximately 80% of the sexually active male and female population. It is passed on through close genital contact. HPV usually has no signs or symptoms but it can facilitate the development of penile, anal, cervical, vulval, vaginal and oro-pharyngeal cancers, as well as genital warts.
There are about 40 types of genital HPV. In most cases, HPV is eliminated by the immune system. HPV infection can sometimes persist. Some HPV types can cause genital warts. Other HPV types (called “high-risk” types) are cofactors that can cause cell changes on a woman’s cervix that can lead to cervical cancer over time.
The types of HPV that cause genital warts are different from the types that can cause cancer. HPV is very different from HIV or herpes infections. HPV does not make it harder to get or stay pregnant. Whilst the cell changes that HPV may cause can be treated, there is no direct treatment for the virus.
HPV vaccination is most effective when given before a person becomes sexually active. It triggers the formation of antibodies to produce immunity and therefore protects the body from disease. The HPV vaccine currently available in Australia is called Gardasil. This vaccine prevents infection with HPV types 16, 18, 6 and 11. HPV 16 and 18 are responsible for the majority (70% internationally; 80% in Australia) of cervical cancers. HPV 6 and 11 are responsible for 90% of genital warts.
- The HPV Vaccine protects against the HPV types that are responsible for the majority of cervical cancers… but no all of the types. Thus, vaccinated patients still need to participate in regular cervical screening.
Another vaccine called Cervarix is available, which protects against the same two high-risk HPV types (types 16 and 18). It does not protect against low-risk HPV types which cause genital warts. Some doctors may recommend this vaccine rather than Gardasil. Which ever vaccination you have, the vaccine will protect those who have never been exposed to these types of HPV.
Understanding the risk ratings of the Cervical Screening Test
- HPV was not detected.
- HPV is required for the development of most cases of cervical cancer.
- Patients at low risk of developing cervical cancer can safely return for a Cervical Screening Test in 5 years.
- HPV detected but not types 16 or 18.
- Liquid based cytology conducted on the same cervical sample was
- Possible LSIL
- or LSIL abnormal cervical cells.
- Not associated with high-grade cell changes that require treatment.
- Repeat HPV test in 12 months to check if the body has cleared the HPV infection.
- HPV not 16/18 detected: Liquid based cytology detects either HSIL or HSIL abnormal cervical cells.
- Patient referred for colposcopic assessment ± cervical biopsy.
- HPV 16/18 detected: Regardless of the Liquid based cytology result
- Patient referred for colposcopic assessment ± cervical biopsy
Unsatisfactory HPV test
- Collect new sample for HPV only in 6-12 weeks.
Unsatisfactory Liquid based cytology test (HPV not 16/18 detected)
- Collect new sample for liquid based cytology only in 6-12 weeks.