Mixed epithelial and mesenchymal tumors

Atypical polypoid adenomyoma

Topic Completed: 1 March 2016

Minor changes: 20 January 2022

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PubMed Search: Atypical polypoid adenomyoma [title]

Vijay Shankar, M.D.
Page views in 2021: 11,522
Page views in 2022 to date: 563
Cite this page: Shankar V. Atypical polypoid adenomyoma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/uterusapa.html. Accessed January 23rd, 2022.
Definition / general
  • Also called APA, atypical polypoid adenomyofibroma
  • Mechanism unclear, but the endometrial stromal cells are considered to be the precursors of the smooth muscle (J Cancer Ther 2011:4:1)
Clinical features
  • Irregular vaginal bleeding
  • Incidental finding in the evaluation of infertility
  • Brownish discharge per vagina rarely
  • May persist or recur, but does not metastasize
  • Patients have increased risk for subsequent carcinoma
  • By histopathological examination
Radiology description
  • T2 weighted images: slightly hyperintense polypoid mass mixed with markedly hyperintense foci that correspond to islands of metaplastic endometrial foci
  • T1 weighted images: tumors are isointense with the myometrium and occasionally have hyperintense cystic foci (J Comput Assist Tomogr 2015;39:32)
Prognostic factors
Case reports
  • Hysterectomy if peri / postmenopausal
  • More conservative management with complete removal of the tumor and close follow up may be considered for women desiring to preserve their fertility (Fertil Steril 2008;89:456, Gynecol Oncol 2013;129:54)
  • The recurrence rate among different modalities of treatment ranges from 10 – 45%
Gross description
  • Resembles endometrial polyp, but often sessile with a broader base
  • Single, well circumscribed, polypoid mass, often in lower uterine segment
  • Very rarely is multiple (Jpn J Radiol 2012;30:606)
  • Usually confined to endometrium with a pushing margin
  • Remaining endometrium is often unremarkable
Gross images

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Polypoid mass

Microscopic (histologic) description
  • Benign biphasic epithelial and mesenchymal tumor
  • Consists of endometrial intraepithelial neoplasm (complex architecture, varying atypia up to severe, cribriform pattern, solid irregular and papillary arrangements), separated by fascicles of bland smooth muscle and fibrous stroma
  • No endometrial type stroma and no prominent stromal atypia
  • Squamous morules are usually present, may have central necrosis
  • Minimal mitotic activity (< 3 per 10 HPF)
  • No desmoplasia
  • Cases with more prominent fibrous appearance may be called atypical polypoid adenofibroma
  • May have coexisting EIN / complex atypical hyperplasia (Diagn Cytopathol 2010;38:527) or well differentiated endometrioid adenocarcinoma (Kobe J Med Sci 2014;60:E74, Gynecol Oncol Case Rep 2012;2:29)
  • Cases with markedly complex glands and architectural complexity are designated as APA of low malignant potential (APA-LMP) (Gynecol Endocrinol 2013;29:623)
Microscopic (histologic) images

AFIP images
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Fascicles of benign, cellular smooth muscle

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Architectural irregularity

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Large benign morules

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Hyperplastic endometrial glands

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Squamous metaplasia

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Crowded glands

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High power

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Cytology description
Positive stains
Molecular / cytogenetics description
Differential diagnosis
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