Cervical Screening Flashcards
How common is HPV infection?
Peak prevalence is 15-25 years
Prevalence declines with age
30% prevalence in young women
What cancer is HPV linked to?
Cervix, penis, vulva/ vagina, anus, mouth and oropharynx
Describe HPV infection in the cervix
Infects the basal cells of the epithelial surface
Micro abrasion allows infection to infect cells
Virus replicates using hosts cellular mechanism
Does not stimulate immune response or tissue trauma
Leads to disorganised cell replication and high grade lesions
What is the timeline of HPV leading to cervical cancer?
90% have cleared papilloma virus infection
In 2 years can lead to persistent HPV infection or viral lesions
In 5 years can lead to pre-cancer potential - CIN 2/3
In 10-20 years then cervical cancer
Describe taking screening samples
Person with a cervix aged 25-64 years
5 yearly smears
Liquid based cytology
Test for high risk HPV
If positive then triage with cytology
Why was there a change to HPV testing for cervical screening?
HPV is more sensitive for high grade abnormalities
HPV is a more effective test for the future
5 year screening interval
What are some features of the HPV test?
Cervical cells
Machine
Identifies infection - could be transient or CIN associated
Sensitive
What are some features of the cytology test?
Cervical cells
Human interpretation
Identifies cellular changes - low grade and high grade
Specific
What is a HPV test?
Molecular test on cells sampled on cervix
Identifies high risk HPV
Targets 14 high risk HPV types
Works on LBC samples
Hybridisation and PCR
What is a cervical cytology sample?
If high risk HPV positive
Microscopic assessment of cells scraped from transformation zone
Look for abnormal cells
Indicate if have cervical intraepithelial neoplasia - CIN
What is dyskaryosis?
Cytology of the cervix which is abnormal
What are the nuclear features of abnormal cells?
Increased size and nuclear : cytoplasmic ratio
Variation in size, shape and course irregular chromatin
Nucleoli
What are the categories of dyskaryosis?
Low grade (+borderline)
High grade
What do koilocytes reflect?
HPV infection
What happens next if positive for hrHPV and dyskaryosis?
Refer to colposcopy
Describe colposcopy
Magnification and light to see cervix
Excludes obvious malignancy
Use of acetic acid - identifies limits of lesion, biopsy site and define area to treat
What are some HPV related pathologies?
HPV infection
Precancerous changes cervical intraepithelial neoplasia (CIN)
Cervical carcinoma
What does E6 and E7 protein products do in the HPV transformation zone?
E7 - prevents cell cycle arrest
E6 - inhibits cell death
What are koilocytosis?
Cells with wrinkled nucleus and perinuclear halo
Multinucleation
What are low risk types of HPV?
6, 11, 42 and 44
Genital warts and low grade CIN
Often transient and resolves
What are high risk types of HPV?
16, 18, 31 and 45
Persistent infection increases risk of developing
High grade CIN and cancer
How does HPV cause high grade CIN?
Persistent infection - viral DNA integrates into host cell genome, overexpression of E6 and 7, and deregulation of host cell cycle
Describe cervical intraepithelial neoplasia
Invisible to naked eye
Disorganised proliferation of abnormal cells in squamous epithelium
CIN 1, 2 and 3
What is CN1?
Low grade dysplasia - will regress
What is CN2?
Moderate dysplasia - may regress
What is CN3?
Severe dysplasia - unlikely to regress
Precursor of invasive cancer
What is the treatment for CIN2/3?
Excise transformation zone of cervix - LLETZ
Ablate transformation zone of cervix - thermal or laser ablation
What is the follow up after treatment of CIN?
Increased risk of cervical cancer so follow up LBC at 6 months for cytology and high risk HPV
Both negative then 3 year recall
If positive - colposcopy
