Salivary glands - Epithelial myoepithelial carcinoma

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Salivary glands

Epithelial / myoepithelial tumors

Epithelial myoepithelial carcinoma

Reviewer: Adriana Handra-Luca, M.D. (see Reviewers page)
Revised: 26 January 2013, last major update September 2012
Copyright: (c) 2003-2013, Pathol2gyOutlines.com, Inc.

General
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● Rare low grade tumor with epithelial and myoepithelial components and frequent local recurrence
● Also called glycogen rich adenoma (clear cell pattern), myoepithelioma (spindle cell and plasmacytoid patterns), myoepithelial carcinoma (if only myoepithelial differentiation and marked cytologic atypia)

Clinical features
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● < 0.5% of salivary gland tumors
● 80% arise in parotid gland
● Mean age 60 years; 60% in women
● Previously considered benign, but with sufficient follow-up, there are rare regional nodal metastases and distant metastases to lung and kidney (Arch Pathol Lab Med 2002;126:676)
● Recurrence related to margin status, angiolymphatic invasion, necrosis, myoepithelial anaplasia
● In overtly malignant cases (cytologic atypia and infiltrative), metastases in 47%, and 29% die of disease after mean 32 months

Case reports
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● 59 year old woman with slow growing parotid tumor (Case of the Week #54)

Gross description
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● Well delineated, firm, infiltration into adjacent tissue
● Usually 2-3 cm

Micro description
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● Low grade with epithelial and myoepithelial components
● Often multinodular with partial thick fibrous capsule
● Most tumor cells have myoepithelial features with clear cytoplasm or naked nuclei
● Focally, there are ducts or tubules with an outer rim of myoepithelial cells and inner, dark ductal cells with scant eosinophilic cytoplasm and round, bland nuclei
● Also islands, nests or sheets of spindle cells, plasmacytoid (hyaline) cells
● Often mild nuclear pleomorphism
● May have high grade transformation / dedifferentiation: overt cytologic malignancy, infiltrative growth and perineurial invasion (Am J Surg Pathol 2010;34:1258)
● Variable mitotic activity; may have ancient change, sebaceous features, Verocay-like change
● Variants include apocrine, dedifferentiated, double clear, ex-pleomorphic adenoma, oncocytic (senescence phenotype), with myoepithelial anaplasia (myoepithelial overgrowth, Arch Pathol Lab Med 2009;133:950)
● Dedifferentiated variant: undifferentiated carcinoma of clear cell, spindle cell, squamous cell type; atypia in >20% cells, no myoepithelial differentiation, older patients, more aggressive behavior, extraglandular and metastastic extension,

Micro images
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Case of week #54

Left to right: AE1-AE3, S100

Well circumscribed, double cell layers, hyalinizing and clear cell patterns

Oncocytic-Sebaceous and Apocrine

Cytology description
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● Cellular, with single cells and naked nuclei
● Biphasic pattern may not be evident since clear cells have fragile cytoplasm and often appear as naked nuclei (Diagn Cytopathol 2003;28:163)

Positive stains
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● Myoepithelial component: PAS+ diastase sensitive due to cytoplasmic glycogen; S100, p63 (Cancer 2005;105:240), smooth muscle actin, smooth muscule myosin heavy chain, vimentin (Am J Surg Pathol 2007;31:44)
● Epithelial component: keratin and EMA (strong), occasional S100; also c-kit, BCL2
● Apocrine variant: AR, GCDFP-15, HER2

Negative stains
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● CEA

Electron microscopy images
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Oncocytic-Sebaceous and Apocrine variants

Differential diagnosis
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● Clear cell carcinoma: usually affects minor salivary glands, unencapsulated, negative for myoepithelial markers
● Malignant mixed tumor
● Metastatic renal cell carcinoma
● Myoepithelial carcinoma: lacks epithelial component (Am J Surg Pathol 2000;24:761)
● Oncocytoma
● Other biphasic tumors include adenoid cystic carcinoma: prominent cribriform pattern and polymorphous low grade adenocarcinoma: affects intraoral salivary glands, clear cells do not predominate, not associated with ductal cells
● Plasmacytoma
● Pleomorphic adenoma: biphasic but with prominent myxochondroid stroma, myoepithelial cells usually lack cytoplasmic clearing
● Skeletal muscle tumors

End of Salivary glands > Epithelial / myoepithelial tumors > Epithelial myoepithelial carcinoma

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