Breast
Epithelial-myoepithelial tumors
Pleomorphic adenoma

Editorial Board Member: Gary Tozbikian, M.D.
Editor-in-Chief: Debra Zynger, M.D.
Shabnam Jaffer, M.D.

Minor changes: 29 September 2020

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PubMed Search: Pleomorphic adenoma [title] breast

Shabnam Jaffer, M.D.
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Cite this page: Jaffer S. Pleomorphic adenoma. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/breastmixedtumor.html. Accessed October 29th, 2020.
Definition / general
  • Biphasic benign breast tumor with varying epithelial and stromal components
Essential features
Terminology
ICD coding
  • ICD-11: 2F30.Y - Other specified benign neoplasm of breast
  • ICD-11: XH2KC1 - Pleomorphic adenoma
Epidemiology
Sites
  • Periareolar, upper outer quadrant
Pathophysiology
  • Breast and salivary glands are embryologically similar exocrine glands that originate from the same ectodermal layer and can differentiate towards dual epithelial myoepithelial cell differentiation
Etiology
Clinical features
Diagnosis
  • Diagnosis may be made on core biopsy or FNA with radiologic correlation but definitive with excision
Radiology description
Radiology images

Contributed by Shabnam Jaffer, M.D., Mark R. Wick, M.D.

Periareolar nodule

Mammogram

Prognostic factors
Case reports
Treatment
Gross description
  • Circumscribed yellow white gritty solid nodules > polypoid, multinodular or satellite lesions
  • Size: typically 0.8 - 4.5 cm (mean = 2.0 cm) (South Med J 1975;68:97)
  • Intraductal nodule with cystification
Gross images

Contributed by Shabnam Jaffer, M.D.

Circumscribed tumor

Microscopic (histologic) description
  • Admixture of epithelial and myoepithelial cells embedded in a chondromyxoid stroma, may show chondroid or osseous metaplasia
  • Architecture includes tubules, islands, cords, trabeculae, sheets or pseudoglandular structures lined by 2 cell types
    • Inner epithelial cells: cuboidal or columnar epithelial cells, with or without apocrine or squamous metaplasia
    • Outer myoepithelial cells: polygonal, plasmacytoid, fusiform or stellate with clear to eosinophilic cytoplasm
  • No atypia, mitoses, necrosis or infiltrative growth
  • Rare malignant transformation
Microscopic (histologic) images

Contributed by Shabnam Jaffer, M.D.

Encapsulated tumor

Biphasic benign tumor

LMWCK

SMA

Virtual slides

Images hosted on other servers:

Myxoid stromal breast tumor

Cytology description
  • Cellular smears consisting of epithelial and myoepithelial cell clusters and sheets arranged in branched glandular structures
    • Epithelial cells: round cells with abundant cytoplasm
    • Myoepithelial cells: stellate, plasmacytoid
  • Stroma: myxochondroid, light green on Pap, metachromatic (red-purple) on Giemsa
  • No atypia, mitoses or necrosis
  • Pitfall for misdiagnosis as mucinous or matrix producing metaplastic carcinoma (Breast Dis 2017;37:105)
Cytology images

Images hosted on other servers:

Hypercellular smears with cohesive fragments

Positive stains
Negative stains
Electron microscopy description
  • Biphasic tumor (Am J Clin Pathol 1990;93:795)
    • Epithelial: microvilli and lumina
    • Myoepithelial: spindled stromal cells with intermediate filaments, dense bodies and intercellular junctions
Molecular / cytogenetics description
Sample pathology report
  • Left breast, mass, lumpectomy:
    • Pleomorphic adenoma, 3.2 cm (see comment)
    • Surgical margins, negative for tumor
    • Comment: The lesion is a circumscribed benign biphasic tumor by morphology and immunohistochemistry. AE1/3 and p63 are expressed. There is associated myxoid stroma. These findings are consistent with pleomorphic adenoma.
Differential diagnosis
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