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Uterus

Non tumor

Endometrial metaplasia


Reviewer: Nat Pernick, M.D. (see Reviewers page)
Revised: 5 March 2012, last major update March 2012
Copyright: (c) 2002-2012, PathologyOutlines.com, Inc.

Subtypes: clear celleosinophilic (oxyphilic)intestinalmucinouspapillarysquamousstromalsyncytialtubal

General

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● Often due to hormonal or irritative stimuli (J Clin Pathol 2011;64:97, Am J Surg Pathol 1980;4:525)
● Must evaluate metaplasia separately from hyperplasia
● Tends to be associated with adenocarcinoma and is more common in women at high risk for endometrial carcinoma

Clear cell metaplasia

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● Tall cells, apical nuclei and clear cytoplasm; no atypia
● Clear cell change by itself is nonspecific
Case reports: with atypical endometrial hyperplasia (
Ann Diagn Pathol 2003;7:381)
DD: clear cell adenocarcinoma

           
Atypical endometrial hyperplasia with clear cell change


Eosinophilic (oxyphilic) metaplasia

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● Also called eosinophilic cell change
● Estrogen-induced, resembles atypical hyperplasia except there is no atypia
● Nonspecific and very common; associated with mucinous metaplasia and ciliated (tubal) change (
Mod Pathol 2005;18:1243)
● MUC5AC+


Eosinophilic cell change and MUC5AC+ in normal proliferative endometrium


Eosinophilic change associated with simple hyperplasia without atypia


Eosinophilic cell change in endometrioid adenocarcinoma


Intestinal metaplasia

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● Rare

Micro images
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Intestinal metaplasia

Positive stains
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● CK20, CDX2, chromogranin, villin (Int J Gynecol Pathol 2011;30:492)


Mucinous metaplasia

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● Resembles endocervical mucosa (Int J Gynecol Pathol 1983;1:383); benign features
● Associated with hyperestrogen states, endometrial polyps
● Multifocal lesions associated with lobular endocervical glandular hyperplasia /pyloric gland metaplasia (Histopathology 2009;54:184)
● May produce mucometra if cervical stenosis present
● Mucin pools are associated with neutrophils

Micro images
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Associated with complex hyperplasia with atypia, HE stain

       
Left: simple mucinous metaplasia in the basalis of an atrophic endometrium
Middle: Complex papillary mucinous metaplasia in curettings
Right: Complex endometrioid hyperplasia with a glandular space lined by micropapillary mucinous metaplasia (arrow)



Mucinous metaplasia in adenocarcinoma


Papillary proliferation / papillary change

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● Rare, usually post-menopausal women
● May be similar to
papillary syncytial change
● Usually benign behavior
● Polypectomy or curettage appears to be adequate treatment (Am J Surg Pathol 2001;25:1347)
● More aggressive treatment may be needed for extensive complex papillary proliferations

Gross description
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● 0.7 cm to 3.0 cm in size, 2/3 occur in endometrial polyps

Micro description
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● Focal areas of fibrovascular cores without atypia, usually near endometrial surface
● Either simple or complex papillary patterns
● Often metaplastic epithelial changes

Micro images
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Papillae are limited to the surface epithelium, and composed of bland uniform lining cells

Cytology description
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● Endometrial glandular and stromal breakdown with papillary metaplasia may resemble well differentiated adenocarcinoma due to similar nuclear size (Diagn Cytopathol 2009;37:487); may have metaplastic clumps with irregular protrusions (Diagn Cytopathol 2006;34:665)

Differential diagnosis
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● Well differentiated / low grade papillary adenocarcinoma


Squamous metaplasia

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● Occurs in normal or hyperplastic endometrium, polyps and leiomyomas; also as part of malignant processes
● Usually diffuse (adenoacanthosis) or in morules (rounded aggregates of bland cells with indistinct cytoplasmic borders)
● Usually in pre-menopausal women with exogenous hormones (
Arch Pathol Lab Med 1995;119:458) or with polycystic ovary disease; also associated with foreign-body reactions, chemical irritants and endometritis
● Note: central necrosis of morules is common and not specific for malignancy
Ichthyosis uteri: complete replacement of endometrium by squamous epithelium; may be associated with malignancy (Diagn Pathol 2006 May 19;1:8)

Micro images
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Squamous metaplasia


Squamous and mucinous metaplasia post-tamoxifen therapy

       
Left: with adenosarcoma; middle: with squamous cell carcinoma; right: with endometrioid carcinoma

Differential diagnosis
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● Well-differentiated endometrial adenocarcinoma with squamous metaplasia


Stromal metaplasia

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● Formation of smooth muscle, cartilage and bone
● May be it difficult to assess myometrial invasion in carcinoma (
Int J Gynecol Pathol 2007;26:115)

Micro images
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Endometrial stromal nodule with smooth muscle metaplasia

Differential diagnosis
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● Retained fetal parts


Syncytial change

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● Also known as papillary syncytial change, surface syncytial change
● Finding in endometrial biopsies and curettings from patients with uterine bleeding
● Associated with anovulatory dysfunctional bleeding, endometrial hyperplasia, estrogen usage or other hormonal treatment
● Appears to be degenerative, not reparative (
Int J Gynecol Pathol 2008;27:534)

Micro description
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● Denuded endometrial surface produced by breakdown or breakthrough bleeding covered by sheet-like plaque of regenerating epithelial cells, often eosinophilic, without discrete cell boundaries (Mod Pathol 2000;13:309)
● Nuclear debris, neutrophils and rounded clumps of endometrial stromal cells usually present
● Usually no papillae with fibrovascular cores
● May resemble microglandular hyperplasia due to small glandular lumina or pseudolumina

Micro images
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Surface syncytial change

   

Surface papillary syncytial change


p16+

Positive stains
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● p16(INK4A) (J Clin Pathol 2011;64:97)


Tubal (ciliated cell) metaplasia

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● Markedly increased ciliated cells (non-metaplastic endometrium have some ciliated cells), resembles fallopian tube; often seen with endometrial hyperplasia and other hyperestrogenic states
● Presence of atypia does not affect prognosis (
Mod Pathol 2011;24:1254)

Micro images
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Hyperplastic endometrium with ciliary change (tubal metaplasia)


Tubal-type ciliated epithelium


Tubal metaplasia


Ciliated (tubal) metaplasia

       

Complex stellate; complex, cribriform glands; mosaic p16 positivity

Positive stains
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● p16 (Cell Oncol 2007;29:37), MUC5AC (52%, Mod Pathol 2005;18:1243)

End of Uterus > Non tumor > Endometrial metaplasia


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