Endometrial hyperplasia
Benign (non atypical) endometrial hyperplasia

Topic Completed: 1 August 2016

Revised: 15 July 2019

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PubMed Search: Benign endometrial hyperplasia

Carlos Parra-Herran, M.D.
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Cite this page: Benign (non atypical) endometrial hyperplasia. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/uterusbenignhyperplasia.html. Accessed August 24th, 2019.
Definition / general
  • Prior to 2014, the World Health Organization classified endometrial hyperplasia as simple versus complex, and nonatypical versus atypical
    • This system suffered from significant interobserver variation (Am J Surg Pathol 2008;32:691)
    • Reproducibility improved with a two tier classification (Histopathology 2014;64:284, Int J Gynecol Pathol 2008;27:318)
    • Accordingly, the classification system was simplified in 2014, and now divides hyperplasia into two categories, benign (nonatypical) hyperplasia and atypical hyperplasia (equivalent to endometrial intraepithelial neoplasia / EIN)
  • The terms "simple" and "complex" have been removed from the classification; they, however, remain in parts of the following text when citing data prior to the 2014 WHO classification

  • Non atypical hyperplasia is part of the spectrum of endometrial changes due to unopposed estrogen stimulation
  • Incidence: 142 per 100,000 woman-years, peaks in early 50s (Am J Obstet Gynecol 2009;200:678)
  • 2 - 4x risk of progression to endometrial carcinoma compared to general population (compared to 45x for atypical hyperplasia / EIN) (Cancer 2005;103:2304)
  • < 1% prevalence of carcinoma diagnosis beyond 1 year after diagnosis of benign endometrial hyperplasia (Mod Pathol 2005;18:324, Hum Pathol 2008;39:866)
Gross description
  • Increased endometrial volume, qualitatively different from normal cycling endometrium
Gross images

Images hosted on other servers:

Endometrial hyperplasia has lush
fronds of hyperplastic endometrium

Microscopic (histologic) description
  • Gland to stroma ratio is greater than 1:1 (glands occupy more than 50% of the surface area); these areas of "gland crowding" still contain small amounts of stroma in between glands, and the individual glandular contours can be easily distinguished
  • Glands are usually round or elongated; however, shape and size irregularity are common including cystic dilation
  • Lining epithelium usually displays proliferative-type morphology with pseudostratified or mildly stratified columnar cells containing elongated cigar shaped nuclei
  • Metaplastic change (tubal, mucinous, squamous, secretory) can be seen
  • Cellular stroma with variable mitotic activity, uniformly distributed blood vessels
  • By definition, there is no cytologic atypia and no significant complexity (glandular confluence with loss of individual glandular contours, cribriform or microacinar architecture)
Microscopic (histologic) images

Images hosted on PathOut servers:

Benign endometrial hyperplasia

Cytology description
Positive stains
Differential diagnosis
  • Artifacts: fragmented endometrium with artificially crowded (compressed) glands
  • Chronic endometritis: may have reactive glandular changes causing abnormal gland shapes and variable metaplasia; but has plasma cells, stromal spindling and edema and surface neutrophils, and gland to stroma ratio < 1:1
  • Cystic atrophy: glandular to stroma ratio is < 1:1, glands lined by flat to cuboidal inactive epithelium, stroma is dense and atrophic
  • Disordered proliferative endometrium: variation in glandular size and shape, metaplasia and patchy breakdown, but with a gland to stroma ratio < 1:1
  • Endometrial polyp: fibrotic stroma with dilated, thick-walled blood vessels
Additional references
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