Endometrial hyperplasia classification

Endometrial hyperplasia is further classified based on histology into simple and complex types. Endometrial hyperplasia can also be classified based on the presence or absence of cellular atypia; hyperplasia with cellular atypia and hyperplasia without cellular atypia.

• Endometrial hyperplasia may be classified based on glandular complexity and nuclear atypicality into the following types:^[1][2][3]

• The updated WHO classification has been proposed to simplify clinical decision making, particularly when making treatment choices.^[4]
  • Simple hyperplasia without atypia
  • Simple hyperplasia is characterized by:
    • Densely packed, cystically dilated, variable sized glands separated by normal intervening stroma ( Figure 10 ). Although
    • 3:1 gland-to-stroma ratio.
    • Ciliated cells
    • Squamous morular metaplasia
  • Complex hyperplasia without atypia
  • Complex hyperplasia without atypia is defined as:
    • Glands with abnormal, irregular architecture set in a background of scant intervening stroma
    • Some stroma must be present,
    • Basement membrane lining individual glands and a rim of intervening endometrial-type stroma between them. In addition to back-to-back and cribriform-like arrangements, other glandular architectural abnormalities warranting designation of complex hyperplasia include
    • Outpouchings,
    • Infoldings, and budding
    • Squamous or morular metaplasia
    • Eosinophilic and ciliated cell changes
  • Simple hyperplasia with atypia
  • Complex hyperplasia with atypia
    • Increased gland-to-stroma ratio (≥3:1)
    • Gland complexity—caused by:
      • Branching
      • Outward budding
      • Internal papillary infoldings
      • Internal bridge
  • Hyperplasia without atypia
  • Atypical hyperplasia/endometrioid intraepithelial neoplasia

Endometrial changes may be classified according to the International Endometrial Collaborative Group into two types:^[5][6]

• Benign hyperplasia (a hormone dependent diffuse lesion, which is polyclonal)
  • Benign endometrial hyperplasia is mostly observed with anovulation or after prolonged exposure to estrogen.
  • The morphology of endometrial hyperplasia varies from proliferative endometrium with a few cysts to heavier endometria with many dilated and contorted glands that are designated as “cystic glandular hyperplasia,” “mild hyperplasia,” or “simple hyperplasia.”

• Endometrial intraepithelial neoplasia
  • Endometrial precancers
  • Epithelial crowding depicts less stromal volume which is approximately half of total tissue volume in non secretory endometrium
  • Typically cells appear morphologically clonal and distinct from the surrounding endometrium.
  • With advanced stage, it may become a more diffuse lesion
  • In the beginning a localized clonal proliferation, which is monoclonal and neoplastic (EIN)
• The D-score is an integral part of the EIN classification :
  • It is a measure of stromal volume as a proportion of total tissue volume (stroma + epithelium + gland lumen)

• The D-score is assigned based on evaluation with computerized morphometry
  • Using this method, specimens are classified as:
    • Benign (D >1)
    • Indeterminate (0< D <1)
    • EIN (D <0).^[7]

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