Epithelial-myoepithelial tumors


Topic Completed: 1 April 2010

Minor changes: 26 August 2020

Copyright: 2002-2022,, Inc.

PubMed Search: Myoepithelioma [title] breast [title]

Hind Warzecha, M.D.
Page views in 2021: 3,936
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Cite this page: Nassar H. Myoepithelioma . website. Accessed January 21st, 2022.
Definition / general
  • Bland spindle cell lesion with myoepithelial phenotype
  • Rare
Clinical features
  • Usually benign, may recur locally
Case reports
Microscopic (histologic) description
  • Dense spindle cell neoplasm, may be arranged in storiform pattern
  • Tumor cells have eosinophilic cytoplasm, oval and regular nuclei
  • May have polygonal cells with clear cytoplasm and hyperchromatic nuclei
  • May infiltrate fat or surround normal ducts
  • No mitotic figures, no necrosis, no atypia
Microscopic (histologic) images

AFIP images

Invasive dense spindle cell lesion

Plump interlacing spindle cells with ovoid nuclei


polygonal cells with

Actin+ spindle
cells with positive
internal control in
normal duct at top

Cytology description
  • Epithelial and spindled cells
  • Mild to moderate nuclear pleomorphism, occasional intranuclear cytoplasmic vacuoles, naked bipolar cells, metachromatic myxoid or fibrillary material
  • No necrosis, no mitotic figures
Positive stains
Negative stains
Electron microscopy description
  • Activated, differentiated myoepithelial cells (cytoplasmic bundles of myofilaments, desmosomes and basal lamina), variable squamous metaplasia (Am J Surg Pathol 1982;6:785)
Differential diagnosis
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