Epithelial-myoepithelial tumors

Myoepithelioma and myoepithelial carcinoma

Last author update: 8 May 2023
Last staff update: 8 May 2023

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PubMed Search: Myoepithelioma

Harsh Batra, M.B.B.S., D.C.P., D.N.B.
Julie M. Jorns, M.D.
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Cite this page: Batra H, Jorns JM. Myoepithelioma and myoepithelial carcinoma. website. Accessed September 30th, 2023.
Definition / general
  • Myoepithelioma: bland spindle cell lesion with myoepithelial phenotype
  • Myoepithelial carcinoma: very rare malignant lesion, mostly arising in association with adenomyoepitheliomas, composed of purely malignant myoepithelial cells, primarily spindle shaped to polygonal
Essential features
  • Myoepithelioma: benign lesion comprised of cells of myoepithelial derivation
  • Myoepithelial carcinoma: rare, malignant tumor of the breast comprised of cells of myoepithelial derivation
ICD coding
  • ICD-O: 8982/3 - malignant myoepithelioma
  • ICD-11:
      • Myoepithelioma:
        • 2F30.Y - other specified benign neoplasm of breast
        • 2F30.Z - benign neoplasm of breast, unspecified
      • Myoepithelial carcinoma:
        • 2C6Z - malignant neoplasms of breast, unspecified
        • 2C6Y & XH43E6 - other specified malignant neoplasms of breast & myoepithelial carcinoma
        • XH43E6 - myoepithelial carcinoma
  • Myoepithelioma: premenopausal and postmenopausal women; wide age range
  • Myoepithelial carcinoma:
    • Incidence is 15 per 100,000 population
    • Mean age for myoepithelial carcinoma in breast: 50 years; range 45 - 86 years (Transl Cancer Res 2017;6:441)
  • Breast, without specific site predilection
  • Tumors that arise from the peripheral myoepithelial cell layer
  • Unknown
Clinical features
  • Myoepithelioma is benign but may recur locally
  • Myoepithelial carcinoma may recur or metastasize to regional lymph nodes or distant sites (Eur J Surg Oncol 2004;30:357)
  • Histologic evaluation of tissue, typically with assistance of immunohistochemistry
Radiology description
  • Mammography: circumscribed or irregular, noncalcified mass
  • Ultrasound: hypoechoic, irregular or oval mass with microlobulated or indistinct margins
  • MRI: enhancing mass with an irregular or spiculated margin and delayed washout or plateau kinetics
  • References: Breast J 2007;13:203, Taehan Yongsang Uihakhoe Chi 2020;81:207
Prognostic factors
  • Myoepithelioma: can recur locally
  • Myoepithelial carcinoma (Eur J Surg Oncol 2004;30:357):
    • Associated with aggressive course, including recurrence and metastasis
    • 2 and 5 year survival is 88% and 55%
    • Increased tumor size is associated with worse outcome
Case reports
  • Myoepithelioma: complete surgical excision (J Cytol 2013;30:62)
  • Myoepithelial carcinoma:
    • Wide local excision, segmental mastectomy or total mastectomy with regional lymph node excision and radiotherapy (Mol Clin Oncol 2016;4:723)
    • Role of chemotherapy is not well defined
    • Platinum analogs and paclitaxel combination has shown some efficacy in few cases reported (Oncologist 2016;21:1492)
Gross description
Microscopic (histologic) description
Microscopic (histologic) images

Contributed by Julie M. Jorns, M.D. and Koteeswaran Govindaswamy, M.D. (Case #407)
Myoepithelioma with adjacent benign glands

Myoepithelioma with adjacent benign glands



Myoepithelial carcinoma Myoepithelial carcinoma Myoepithelial carcinoma

Myoepithelial carcinoma

Myoepithelioma - p63

Myoepithelioma - p63

Tumor cells positive for p63 IHC

Myoepithelial carcinoma - p63

Tumor cells positive for CK 5/6 IHC

Myoepithelial carcinoma - CK 5/6

Tumor cells positive for pan CK IHC

Myoepithelial carcinoma - pan CK

Tumor cells positive for Ki67 IHC with high Ki67 index (approx. 15-20/hpf)

Myoepithelial carcinoma - Ki67 IHC with high Ki67 index

Tumor cells are negative for ER, positive for PR and negative for Her2Neu

Myoepithelial carcinoma - tumor cells are negative for ER, positive for PR and negative for Her2Neu

Cytology description
Cytology images

Images hosted on other servers:

Myoepithelioma FNA

Positive stains
Negative stains
Electron microscopy description
Molecular / cytogenetics description
Molecular / cytogenetics images

Images hosted on other servers:

Summary karyogram 10 cases

Sample pathology report
  • Left breast, core biopsy:
    • Spindle cell neoplasm (see comment)
    • Comment: Histologic sections show a spindle cell neoplasm arranged in storiform pattern. The tumor cells have vesicular nuclei, prominent nucleoli, variable nuclear atypia and eosinophilic cytoplasm. Mitoses are readily identifiable (with up to 4 mitoses/10 high power fields). Focal areas of cystic degeneration and necrosis are seen. Immunohistochemistry shows tumor cells to be positive for p63 and cytokeratins 5/6 and 903 and negative for cytokeratin 7, desmin, ER, PR and HER2 / neu. Overall, findings are suggestive of metaplastic carcinoma, spindle cell type or myoepithelial carcinoma.
Differential diagnosis
  • Metaplastic carcinoma:
    • Variable group of breast carcinomas with mesenchymal differentiation
    • Myoepithelial carcinoma is considered a subtype by WHO
  • Spindle cell sarcoma:
    • Negative for myoepithelial markers
  • Leiomyosarcoma:
    • Blunt ended nuclei with abundant cytoplasm
    • Positive for desmin
  • Fibromatosis:
    • Infiltrative fibroblastic and myofibroblastic proliferation
    • Minimal pleomorphism with no mitosis
    • Positive for actin, desmin and S100
    • Negative for cytokeratins
  • Adenomyoepithelioma:
    • Biphasic, circumscribed tumor composed of variable number of myoepithelial cells surrounding epithelial lined spaces
  • Myofibroblastoma:
    • Cellular, collagenized, epithelioid, palisaded, lipomatous and hemangiopericytoma-like, with infiltrative features
    • Positive for vimentin, CD34 and desmin
Board review style question #1

Biopsy of a breast nodule showed the histology in the image above. All tumor cells are strongly and diffusely positive for p63. What is the most likely diagnosis?

  1. Adenoid cystic carcinoma
  2. Adenomyoepithelioma
  3. Myoepithelial carcinoma
  4. Myoepithelioma
Board review style answer #1
C. Myoepithelial carcinoma. The biopsy shows an atypical proliferation with plump spindle cells and readily identifiable mitoses. p63 positivity supports myoepithelial differentiation. The morphology is malignant, arguing against adenomyoepithelioma and myoepithelioma. Adenomyoepithelioma and adenoid cystic carcinoma additionally have a biphasic composition, making these answers incorrect. In this case, tumor cells are of uniform myoepithelial differentiation, making the best diagnosis myoepithelial carcinoma, which is considered a metaplastic carcinoma of no special type by the WHO.

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Reference: Myoepithelioma and myoepithelial carcinoma
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