Cervix
Premalignant / preinvasive lesions
Squamous intraepithelial lesions (SIL) - general

Author: Seema Khutti, M.D. (see Authors page)

Revised: 14 April 2017, last major update December 2013

Copyright: (c) 2003-2017, PathologyOutlines.com, Inc.

PubMed Search: squamous intraepithelial lesion [title ]cervix
Cite this page: Squamous intraepithelial lesions (SIL)-general. PathologyOutlines.com website. http://pathologyoutlines.com/topic/cervixSIL.html. Accessed April 27th, 2017.
Definition / General
  • Squamous intraepithelial lesions are defined as squamous alterations in the cervical transformation zone that are induced by HPV infection
  • Differences in the differentiation level or differentiation pathway of the underlying mucosa may influence the morphologic presentation, leading to additional patterns not accounted in traditional classifications.
  • See Table 1 below for summary of lesion categories:
Terminology
  • In 1975, for the first time, WHO proposed unified terminology to describe and report precursor lesions in cervical biopsy
  • In 1980, the International Society of Gynecologic Pathologists (ISGYP) replaced the term dysplasia with CIN
  • Most recent and widely used nomenclature is based on The Bethesda System, a two tiered system, LGSIL and HGSIL
  • In the vaccine era and with the application of biomarkers or new algorithms, CIN 2, conceivably may be viewed more critically to allow for conservative management of subset of women with this diagnosis
Epidemiology
  • Predominantly a disease of women in reproductive years
  • Risk factors are similar to squamous cell carcinoma: sexual activity before age 17 years, multiple sexual partners, HPV infection, HLA subtypes, immunosuppression, smoking
Sites
  • Transformation zone
  • Lesion may have abrupt borders or extend up endocervical canal
Diagrams / Tables

Images hosted on other servers:

Table 1: Summary
of lesion categories;
LR: low risk; HR: high risk

Treatment
  • LSIL:
    • Controversial since most lesions regress
  • HSIL:
    • Cone
    • LEEP
    • Electrodiathermy
    • Cryosurgery
    • Laser
    • Long term followup is necessary
  • Note:
Prognostic factors for recurrence after LEEP
Gross Description
  • Identified best with colposcopic examination after application of acetic acid
  • More common on anterior lip of cervix than posterior lip
  • Rarely occurs laterally
Micro Description
  • Impact of HPV infection on squamous epithelium is summarized in two parameters:
    1. Alterations in the density of superficial epithelial cells
      • Persistence of higher nuclear density manifested by either more nuclei per unit area or more nuclear area
    2. Superficial squamous atypia
      • In mature SIL, HPV infection produces nuclear enlargement, variation in nuclear size, and binucleation
  • Histopathologic features of CIN (with progressively more abnormal degrees)
    1. Nuclear abnormalities: N/C ratio (↑), hyperchromasia (↑), nuclear pleomorphism and anisokaryosis (↑), irregular nuclear polarity (↑), wrinkling of nuclear membranes (↑)
    2. Mitotic activity: number of mitotic figures (↑), height in epithelium (relation to surface) (↑), abnormal configurations (↑)
    3. Differentiation: Proportion of epithelium showing differentiation (↓), proportion of unit area occupied by nuclei (↑)
Features to report:
  • LSIL or HSIL (or use terminology at institution)
  • Presence of endocervical glandular involvement
  • Presence in multiple quadrants
  • Presence of HPV related changes
  • Margin involvement (including endocervical margin)
  • Involvement of endocervical clefts
Micro Images

SIL diagram

Classification systems

Cytology Description
Positive Stains