Endometrial hyperplasia classification

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Swathi Venkatesan, M.B.B.S.[2]


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.


The World Health Organization (WHO) Classification System

The WHO Classification (1994)

Endometrial hyperplasia
Simple hyperplasia with cellular atypia
Simple hyperplasia without cellular atypia
Complex hyperplasia with cellular atypia
Complex hyperplasia without cellular atypia

The New WHO Classification (2014)

  • 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:
    • 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

The Endometrial Intraepithelial Neoplasia (EIN) Classification

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]


  1. Scully RE. Histological typing of female genital tract tumours. Springer; 1994.
  2. Endometrial hyperplasia. Radiopedia. http://radiopaedia.org/articles/endometrial-hyperplasia-1 Accessed on March 3, 2016.
  3. Jorizzo JR, Chen MY, Martin D, Dyer RB, Weber TM (2002). "Spectrum of endometrial hyperplasia and its mimics on saline hysterosonography". AJR Am J Roentgenol. 179 (2): 385–9. doi:10.2214/ajr.179.2.1790385. PMID 12130438.
  4. Emons G, Beckmann MW, Schmidt D, Mallmann P, Uterus commission of the Gynecological Oncology Working Group (AGO) (2015). "New WHO Classification of Endometrial Hyperplasias". Geburtshilfe Frauenheilkd. 75 (2): 135–136. doi:10.1055/s-0034-1396256. PMC 4361167. PMID 25797956.
  5. Mutter GL (2000). "Endometrial intraepithelial neoplasia (EIN): will it bring order to chaos? The Endometrial Collaborative Group". Gynecol Oncol. 76 (3): 287–90. doi:10.1006/gyno.1999.5580. PMID 10684697.
  6. Baak JP, Mutter GL (2005). "EIN and WHO94". J Clin Pathol. 58 (1): 1–6. doi:10.1136/jcp.2004.021071. PMC 1770545. PMID 15623473.
  7. Baak JP, Ørbo A, van Diest PJ, Jiwa M, de Bruin P, Broeckaert M, Snijders W, Boodt PJ, Fons G, Burger C, Verheijen RH, Houben PW, The HS, Kenemans P (July 2001). "Prospective multicenter evaluation of the morphometric D-score for prediction of the outcome of endometrial hyperplasias". Am. J. Surg. Pathol. 25 (7): 930–5. PMID 11420465.

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