Skin - Nonmelanocytic tumors
Adnexal tumors - eccrine sweat glands

Author: Christopher Hale, M.D. (see Authors page)

Revised: 6 October 2016, last major update June 2012

Copyright: (c) 2002-2016,, Inc.

PubMed Search: Myoepithelioma [title]

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Cite this page: Myoepithelioma. website. Accessed March 25th, 2019.
Definition / general
  • Tumors with myoepithelial cells but no epithelial cells (Hum Pathol 2004;35:14)
  • Usually benign lesions of extremities, but should be completely excised
  • May recur locally, rarely metastasize
  • Usually male, mean age 22 years (range 10 - 63 years)
  • Part of a continuum with mixed tumors (ductal structures but few myoepithelial cells)
  • Mitotic activity may predict more aggressive tumor
Gross description
  • Mean 1 cm, range 0.5 to 2.5 cm
Microscopic (histologic) description
  • Well circumscribed dermal lesions, not connected to epidermis, may extend into superficial subcutis
  • Either composed of:
    • Solid proliferation of ovoid, spindled, histiocytoid or epithelioid cells with abundant eosinophilic syncytial cytoplasm and little stroma; or
    • Reticular architecture with epithelioid, plasmacytoid or spindle cells in myxoid or hyalinized stroma
  • Cells have ovoid / spindled nuclei, mild pleomorphism, small necrotic areas, fatty metaplasia, minimal mitotic figures (0 - 6 / 10 HPF), no ductal differentiation
Microscopic (histologic) images

Images hosted on other servers:

Various images

Positive stains
Differential diagnosis
  • Benign mixed tumor
  • Cellular neurothekeoma: nested architecture, sclerotic dermal collagen, NKI-C3+, S100-, EMA-, keratin-
  • Epithelioid benign fibrous histiocytoma: lower limbs, circumscribed, polypoid, plump and often binucleate epithelioid cells, may entrap dermal collagen, keratin-, myogenic markers-, S100-
  • Epithelioid sarcoma: distal extremities of young adults, infiltrates along fibrous septa and fascial planes, discontinuous growth, S100-, GFAP-
  • Leiomyoma
  • Myoepithelial carcinoma
  • Spitz nevus: large epithelioid melanocytes with prominent nucleoli, junctional component, downward maturation, HMB45+, S100+, EMA-, keratin-, myogenic markers-
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