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Atypia / premalignant / preinvasive lesions

LSIL / CIN I / low grade dysplasia

Reviewers: Marilin Rosa, M.D., University of Florida (see Reviewers page)
Revised: 2 May 2014, last major update June 2011
Copyright: (c) 2002-2011, PathologyOutlines.com, Inc.


● Low grade squamous intraepithelial neoplasia (LSIL) encompasses HPV changes and cervical intraepithelial neoplasia I (CINI)
● Previously called mild dysplasia

Clinical features

● Cases with few abnormal cells are more likely to be missed (Arch Pathol Lab Med 2005;129:23)
● HPV negative LSIL is not a distinct biologic entity; often due to false positive LSIL or false negative HPV; HPV tests are designed to detect high risk HPV, not the low risk HPV that cause LSIL (Cancer 2005;105:253)
● HPV16+ LSIL or ASC have higher risk for HSIL than HPV16 negative LSIL/ASC (J Natl Cancer Inst 2005;97:1066)
● Most LSIL cases during pregnancy remain stable or regress, but most HSIL cases diagnosed antepartum persist postpartum and 11% progress to invasive carcinoma (Cancer 2004;102:228)
● LSIL diagnostic accuracy is improved by Ki-67 staining

Cytology description

● Enlarged nuclei at least 3x size of nucleus of intermediate cell, but N/C ratio is less than 1/3
● Hyperchromasia (nuclei darker than that of intermediate cell), cell may be enlarged (largest atypical cells in gynecologic cytology are LSIL), slight increase in N/C ratio
● No nucleoli
● Binucleation is more common than multinucleation
● Koilocytes may be present, and exhibit nuclear pleomorphism, wrinkled nuclei, hyperchromasia, binucleation, perinuclear halos with distinct clear zone around nucleus and condensation of denser cytoplasm around the periphery
● Cytology from immature LSIL may be interpreted as metaplasia, ASCUS or HSIL
● Few/no mitotic figures, particularly in lower half of epithelium; no atypical mitotic figures

Cytology images

Various images

Contributed by: Marilin Rosa M.D, University of Florida

Virtual slides

Low grade SIL #3; #4

Differential Diagnosis

Reactive epithelial changes: cytoplasmic halos are associated with glycogenated cells, mild atypia is associated with inflammation, but no pleomorphism is present; small binucleated cells may be seen in a background of metaplasia; reactive changes usually have regular nuclear spacing, distinct nucleoli, no nuclear atypia in upper layers, superficial maturation
Postmenopausal squamous atypia: pseudokoilocytosis with uniform/round halos with central nuclei, slightly hyperchromatic, occasional grooves, occasional binucleation; is associated with urothelial metaplasia and atrophy; is NOT associated with HPV (Mod Pathol 1995;8:408)

End of Cervix-cytology > Atypia / premalignant / preinvasive lesions > LSIL / CIN I / low grade dysplasia

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