CIN and mimics

1. CIN and mimics Dr Michael Coutts Consultant GynaecologicalPathologist West Kent GynaeOncology Centre, Maidstone, UK and Centre Hospitalier Universitaire, Nice, France

2. Cervical intraepithelialneoplasia (CIN) • Abnormal proliferation, nuclear atypia and lack of maturation of squamous cells within the epithelium

3. Natural history of CIN • Conflicting data from various studies, however: • 90% of CIN 1 regresses in 2 years • 50% of CIN 2 regresses in 2 years • Approx 10% of CIN 1 and 20% of CIN 2 will progress to CIN 3 • Approx 30% of CIN 3 will regress but roughly 20% will progress to invasive squamous ca • Mean time for progression from CIN to invasive cancer approx 10 – 20 years

4. Human papillomavirus (HPV) • Present in 99.7% of cervical cancer • A causative agent for virtually all cervical cancer (and CIN and CGIN/ACIS) • 55nm non-enveloped DNA virus

5. Human papillomavirus • Over 100 sub-types according to gene sequence of L1 capsid protein • Highest risk 16, 18, 31, 45 • HPV 16 and 18 together cause 70% of cervical cancer • HPV infection starts at TZ (squamocolumnar junction) • Most HPV infection is cleared by the immune system but a minority progresses to CIN or invasive carcinoma • Factors influencing progression include HPV type, viral load, host immunity, parity, smoking, oral contraceptives

6. Infection with HPV <10% >90% 15-25 yrs Lesions Asymptomatic infection Koilocytosis and CIN 1 Most 20% CIN 2 Elimination of virus Regression of lesions 20% ? Appx 30% regression of CIN2/3 Effective immune system CIN 3 20% progression If untreated Invasive carcinoma Normal cervix

7. CIN 1 (LSIL) • Nuclear atypia with mitoses and a high N:C ratio confined to the lower 1/3 • Koilocytosis most obvious in the upper levels of epithelium

8. Koilocytosis • Perinuclear clearing which is sharply defined • Eccentric, hyperchromatic nucleus with coarse chromatin • Nuclei may be multinucleate or raisin-shaped

9. Koilocytosis without CIN (LSIL)

10. Condyloma acuminatum • Benignpapillomacaused by HPV • Usuallylowrisk 6, 11 • More common on vulva • Cauliflower-likegrowth of fibrovascularcoreslined by squamousmucosawithkoilocytosis, parakeratosis • Essentially LSIL, but occasionally high grade CIN mayoccur in a condyloma

11. CIN 2 (HSIL) • Nuclearatypiawithfailure of maturation and mitoses in lower 2/3 • Abnormal mitoses maybeseen • Koilocytosis in upperlayers

12. CIN 3 (HSIL) • Nuclear atypia with failure of maturation in upper 1/3 • Abnormal mitoses • Koilocytes hard to find • No invasion

13. CIN 3

14. CIN 3

15. CIN 3 in endocervical crypt

16. Keratinising CIN 3

17. Pleomorphic CIN 3

18. Immunohistochemistry in CIN 3 p16 Ki67

19. Mimics of CIN: Immature metaplasia • Stratifiedlayers of cellswithlittle maturation (a high N:C ratio) whichmayextendintocrypts But: • Nucleievenlyspaced, withoutmuchcrowding • Regular nuclearoutline, withoutcoarsechromatin • Lowmitotic rate, withoutabnormalforms • Layer of residual endocervical epitheliummaybepresent on the surface (rare over high grade CIN)

20. Mimics of CIN:Immature squamousmetaplasia

21. Mimics of CIN: Immature metaplasia

22. Immunohistochemistry of immature squamousmetaplasia Ki67 p16

23. Mimics of CIN: Atrophy • Stratified layer of cellswithlittle maturation (iewith a high N:C ratio) But: • Epitheliumisthin • Nuclei are evenlyspaced, withoutcrowding • Nuclearpleomorphism and mitoses are absent • Nucleimaybeovoidwith longitudinal grooves (so-called ‘transitionalmetaplasia’, probably a variant of atrophy)

24. Mimics of CIN: Atrophy

25. Mimics of CIN:Atrophy and inflammation

26. Mimics of CIN: Reactive, inflammatory changes • Inflammation can cause nuclearenlargement, nucleolarprominence and scatteredmitotic figures But: • Pleomorphismismild and N:C ratio generallynormal • Mitoses are few and only in lowerlayers • Nucleolarprominenceis not a typicalfeature of CIN • Acute and chronicinflammatorycells are present in the epitheliumtogetherwithintercellularoedema • Mildperinuclear clearing of squamouscellsmaybeseen as an inflammatoryphenomenon

27. Mimics of CIN: Inflammation(withatrophy and tangentialsectioning)

28. Mimics of CIN: inflammation

29. Inflamed CIN 3

30. Mimics of CIN: diathermy artefact • Artefact in surface epithelium adjacent to resection margins due to heat from the loop • Nuclear hyperchromasia and elongation • Changes most marked in the basal layers with the overlying surface epithelium often normal • Mitoses not identified • Adjacent epithelium often normal • Low immunohistochemical staining with Ki67

31. Mimics of CIN: Diathermy artefact

32. Mimics of CIN: tangentialsectioning • Poor orientation of the biopsy during paraffin embedding so that the histological section is not 90° to the epithelial surface • The basal layer is sectioned obliquely so that it appears thicker than normal and gives a false impression of lack of maturation • However, cellular spacing is generally even, without crowding • Deeper levels cut from the block may clarify the overall architecture of the lesion

33. Mimics of CIN: tangentialsectioning

34. Mimics of CIN: tangentialsectioning

35. Tangentialsectioning (deeperlevels)

36. Conclusions • HPV infection is common but only a minority progresses to CIN or invasive carcinoma • This progression is slow and so CIN can be detected by screening before invasion occurs • CIN is graded 1 to 3 • Mimics of CIN include immature squamous metaplasia, atrophy, inflammation, diathermy artefact, tangential sectioning