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Uterus

Carcinoma

Endometrial intraepithelial neoplasia (EIN)

Reviewer: Nat Pernick, M.D. (see Reviewers page)
Revised: 1 December 2011, last major update December 2011
Copyright: (c) 2002-2011, PathologyOutlines.com, Inc.

General
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● Classification system (Gynecol Oncol 2000;76:287) for a precursor to endometrioid endometrial adenocarcinoma
● An alternative to the WHO system of complex or simple hyperplasia with or without atypia
● Most EIN cases are monoclonal and thus premalignant

Criteria for EIN includes:
● A larger glandular area than stromal area (volume percent stroma < 55%)
● Cytology differs between the crowded glandular focus and the background glands
● The premalignant area is at least 1 mm

Clinical features
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● Rare finding without invasive carcinoma; may be associated with extrauterine disease
● Usually cured by hysterectomy if NO extrauterine involvement by careful staging
● May be precursor of invasive serous carcinoma
● Must also exclude progesterone related effects (wait 2-4 weeks after cessation of hormones), benign mimics (disordered proliferative endometrium or atrophy) and carcinoma
● Prediction of progression versus WHO system varies by study from more accurate (Cancer 2005;103:2304) to similar (Cancer 2008;113:2073)
● May better classify patients into high and low risk subgroups (Mod Pathol 2005;18:324)
● Serous endometrial intraepithelial carcinoma arising in adenomyosis is rare (Int J Gynecol Pathol 2011;30:271); serous EIC may be preceded by p53 signature (Mod Pathol 2009;22:345)

Case reports
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● 45 year old woman with menometrorhagia (Case of the Week #60)

Micro description
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● Replacement of benign surface endometrium and underlying glands with high-grade malignant cells that may resemble serous carcinoma
● No evidence of invasion
● Often involves benign endometrial polyps with extensive replacement of surface epithelium and glands

Micro images
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Endometrial intraepithelial carcinoma

               
Various images

   
Clear cell variant: left - H&E, p53 and Ki-67; right - clear cell endometrial glandular dysplasia and clear cell EIC

   
Serous EIC and possible precursor lesions


p53 staining

Positive stains
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● p53, Ki-67

Additional references
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● J Clin Pathol 2002;55:326, Am J Surg Pathol 2000;24:797, Am J Surg Pathol 2000;24:726

End of Uterus > Carcinoma > Endometrial intraepithelial neoplasia (EIN)

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