Endometrial hyperplasia
Benign (non atypical) endometrial hyperplasia

Topic Completed: 1 August 2016

Revised: 15 October 2019

Copyright: 2002-2019, PathologyOutlines.com, Inc.

PubMed Search: Benign endometrial hyperplasia

Carlos Parra-Herran, M.D.
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Cite this page: Parra-Herran C. Benign (non atypical) endometrial hyperplasia. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/uterusbenignhyperplasia.html. Accessed December 11th, 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

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

AFIP images

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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