Salivary glands
Primary salivary gland neoplasms
Malignant
Epithelial myoepithelial carcinoma


Topic Completed: 22 April 2021

Minor changes: 22 April 2021

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PubMed Search: Epithelial myoepithelial carcinoma[TI] salivary glands

Ruta Gupta, M.B.B.S., M.D.
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Cite this page: Huang ML, Gupta R. Epithelial myoepithelial carcinoma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/salivaryglandsepimyocarcinoma.html. Accessed May 16th, 2021.
Definition / general
  • Uncommon malignant biphasic salivary gland neoplasm composed of luminal ductal cells surrounded by myoepithelial cells
Essential features
  • Rare primary salivary gland neoplasm
  • Biphasic neoplasm with a combination of both epithelial and myoepithelial elements
  • Generally good prognosis; poorer prognosis associated with minor salivary gland location, large tumor (> 4 cm), high proliferation index, margin status, high grade transformation
Terminology
  • Adenomyoepithelioma (not recommended)
ICD coding
  • ICD-0: 8562/3 - Epithelial myoepithelial carcinoma
Epidemiology
Sites
Pathophysiology
  • Presumed to be of intercalated duct origin
  • Up to 85% of epithelial myoepithelial carcinomas carry an HRAS mutation (Am J Surg Pathol 2019;43:984)
Etiology
Clinical features
  • Slow growing, painless mass
  • Usually unilateral
  • Rarely presents with facial nerve palsy and lymphadenopathy, may indicate high grade transformation (Medicine (Baltimore) 2017;96:e8988)
Diagnosis
  • Clinical examination and investigations such as magnetic resonance imaging and fine needle aspiration generally do not provide a definitive preoperative diagnosis
Prognostic factors
  • Mean survival up to 165 months; another group found up to 81% of patients to be disease free at 15 years (BMC Ear Nose Throat Disord 2018;18:15, Otolaryngol Head Neck Surg 2015;153:569)
    • Univariate tumor related predictors of lower disease free survival include margin status, lymphovascular invasion, tumor necrosis, myoepithelial anaplasia (> threefold variation in size, irregular nuclear membranes, coarse chromatin, macronucleoli) (Am J Surg Pathol 2007;31:44)
    • Multivariate patient related predictors of lower disease free survival include > 80 years at time of diagnosis, worse in African American population, nonsurgical treatment (BMC Ear Nose Throat Disord 2018;18:15)
  • Poorer prognosis associated with minor salivary gland location, large tumor (> 4 cm), high proliferation index, margin status, high grade transformation (Am J Surg Pathol 2010;34:1258)
Case reports
Treatment
Gross description
Gross images

Contributed by Ruta Gupta, M.B.B.S., M.D.
Solid tumor

Solid tumor

Frozen section description
  • Should not be used; a reliable diagnosis of epithelial myoepithelial carcinoma may not be possible on frozen section
Microscopic (histologic) description
  • Bilayered arrangement of small luminal cells with eosinophilic cytoplasm and outer myoepithelial cells with clear cytoplasm rich in glycogen (diastase sensitive PAS+)
  • A few morphologic types may be seen, depending on the proportion of epithelial and myoepithelial cells present
    • Classic
    • Epithelial dominant
    • Myoepithelial dominant
  • Tubular, glandular, solid growth patterns
  • Papillary and cystic areas may also be present (Am J Surg Pathol 2019;43:984)
  • Basement membrane-like hyalinized matrix may be present
  • Myoepithelial component can often be spindled or have clear cells
  • High grade transformation (20%) infers poorer prognosis (Head Neck Pathol 2013;7:S37)
    • Usually the epithelial component
    • Sheets and solid nests of markedly atypical cells with increased mitoses and necrosis
  • Other morphological variants
  • Rare findings of squamous, sebaceous differentiation as well as ancient and Verocay-like change (Arch Pathol Lab Med 2009;133:950)
Microscopic (histologic) images

Contributed by Ruta Gupta, M.B.B.S., M.D.
Nodular growth pattern

Nodular growth pattern

Biphasic morphology

Biphasic morphology

Biphasic pattern

Biphasic pattern

Spindled myoepithelial cells

Spindled myoepithelial cells

Clear myoepithelial cells

Clear myoepithelial cells

Virtual slides

Images hosted on other servers:
Epithelial myoepithelial carcinoma

Epithelial myoepithelial carcinoma

Cytology description
  • Cytology is not reliable, has a high false negative rate (Cancer Cytopathol 2020;128:392)
    • Most cases may be misdiagnosed as pleomorphic adenoma due to overlapping cytological features
  • Biphasic clusters of ductal cells admixed with larger clear myoepithelial cells
  • Background naked myoepithelial nuclei with scant stromal fragments
  • Occasional globules of hyalinized basal luminal material (Diagn Cytopathol 2003;28:163)
  • Generally bland cytological features
Positive stains
Negative stains
Electron microscopy description
  • Usually not required for diagnosis
  • Ductal cells attached with junctional complexes and desmosomes and showing microvilli on luminal surface (J Med Assoc Thai 1998;81:712)
  • Myoepithelial cells contain abundant glycogen (electron lucent) with cytokeratin filaments, subplasmalemmal plaques and multilayered basal lumina
Molecular / cytogenetics description
Sample pathology report
  • Left parotid, excision:
    • Epithelial myoepithelial carcinoma (see comment)
    • Comment: There is a lobulated and unencapsulated biphasic primary neoplasm. The tumor shows a nodular growth pattern. The tumor is composed of bilayered arrangement of small luminal cells with eosinophilic cytoplasm and outer polygonal clear, rich in glycogen (diastase sensitive PAS+) myoepithelial cells. Immunohistochemically the inner epithelial cells are positive for AE1 / AE3 and EMA, while the outer myoepithelial layer shows staining for p63, smooth muscle actin and S100. There is no evidence of necrosis or high grade transformation.
Differential diagnosis
Board review style question #1

A 65 year old woman presented with a 3 month history of unilateral cheek lump that recently increased in size. A histologic image of the resection is provided above. What is the most common histological feature associated with this lesion?

  1. Anaplasia
  2. High proliferation index
  3. Lymphovascular invasion
  4. Necrosis
  5. Perineural invasion
Board review style answer #1
E. Perineural invasion

Comment Here

Reference: Epithelial myoepithelial carcinoma
Board review style question #2
Which of the following immunohistochemical combinations is most helpful in diagnosing epithelial myoepithelial carcinoma?

  1. AE1 / AE3, CD117 and p63
  2. AE1 / AE3, EMA and CK7
  3. AE1 / AE3, S100 and p63
  4. Nuclear beta catenin
  5. p63, SMA and calponin
Board review style answer #2
C. AE1 / AE3, S100 and p63

Comment Here

Reference: Epithelial myoepithelial carcinoma
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