Salivary glands - Myoepithelioma

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Salivary glands

Epithelial / myoepithelial tumors

Myoepithelioma

Reviewer: Adriana Handra-Luca, M.D. (see Reviewers page)
Revised: 29 January 2013, last major update September 2012
Copyright: (c) 2003-2013, PathologyOutlines.com, Inc.

General
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● Rare benign tumor composed only of myoepithelial cells
● Formerly considered a variant of pleomorphic adenoma
● See also epithelial-myoepithelial carcinoma

Clinical features
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● 1% of salivary gland tumors, more common in parotid and minor salivary gland tumors
● Mean age 54 years, also children
● May be associated with myasthenia gravis
● Recur locally if incomplete removal
● Imaging: well circumscribed, lobulated, inhomogeneous enhancement, apparent diffusion coeficient on MRI different from Warthin tumor and similar to pleomorphic adenoma (AJNR Am J Neuroradiol 2009;30:591)

Case reports
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● 29 year old woman with plasmacytoid myoepithelioma of palate (Head Neck Pathol 2011;5:154)
● 80 year old man with cystic clear cell myoepithelioma of parotid gland (Oral Maxillofac Surg 2009;13:45)

Clinical images
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Plasmacytoid myoepithelioma of minor salivary glands

Gross description
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● Up to 5 cm; encapsulated, may have cystic change

Micro description
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● Solid (nonmyxoid), myxoid (pleomorphic adenoma-like), reticular (canalicular-like) or mixed patterns of myoepithelial cells with no ductal differentiation
● Plasmacytoid cells, spindle cells, clear cells, epithelioid cells, oncocytic cells, hyaline cells
● Mucoid or hyaline stroma, rarely lipomatous
● Rarely synchronous with adenoid cystic carcinoma
● Rarely with intracapsular invasion

Micro images
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Plasmacytoid myoepithelioma of palate

Plasmacytoid myoepithelioma of minor salivary glands

Myoepithelioma of minor salivary gland of cheek

Cytology description
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● Nuclear grooves, intranuclear cytoplasmic inclusions, nuclear striations (zebra lines), myxoid matrix; no marked pleiomorphism, no mitoses

Positive stains
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● Vimentin, GFAP, S100, calponin (Braz Dent J 2007;18:192), HHF35, CD10, cytokeratin 5/6, CK7, CK14, CEA
● Also muscle specific actin

Negative stains
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● CEA, p53, HER2

Molecular / cytogenetics description
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● Aneuploid or diploid, 12q alterations, chromosome 8q involved in malignant phenotype

Differential diagnosis
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● Epidermal cyst: similar clinically
● Squamous cell carcinoma
● Undifferentiated carcinoma
● Warthin tumor: similar on ultrasound

End of Salivary glands > Epithelial / myoepithelial tumors > Myoepithelioma

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