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Table of Contents
Definition / general | Clinical features | Case reports | Gross description | Microscopic (histologic) description | Microscopic (histologic) images | Cytology description | Positive stains | Negative stains | Electron microscopy images | Differential diagnosisCite this page: Handra-Luca A. Epithelial myoepithelial carcinoma. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/salivaryglandsepimyocarcinoma.html. Accessed June 16th, 2019.
Definition / general
- 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
- < 0.5% of salivary gland tumors
- 80% arise in parotid gland
- Mean age 60 years; 60% in women
- Previously considered benign but with sufficient followup, 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
- 59 year old woman with slow growing parotid tumor (Case of the Week #54)
Gross description
- Well delineated, firm, infiltration into adjacent tissue
- Usually 2 - 3 cm
Microscopic (histologic) description
- 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
Microscopic (histologic) images
Case of the Week #54
Various images
AE1 / AE3
S100
Images hosted on other servers:
Oncocytic-sebaceous and apocrine
Cytology description
- 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
- Myoepithelial component: PAS+ diastase sensitive due to cytoplasmic glycogen; S100, p63 (Cancer 2005;105:240), smooth muscle actin, smooth muscle 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
Electron microscopy images
Images hosted on other servers:
Oncocytic-sebaceous and apocrine variants
Differential diagnosis
- 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
- 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
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