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epithelial-myoepithelial carcinoma

Thursday 2 September 2010

EMC; EMCA

WKP

Definition: Epithelial-myoepithelial carcinoma (EMC) is a rare salivary gland tumor of presumed intercalated duct origin with a low risk of metastasis and mortality.

Epithelial myoepithelial carcinoma of parotid gland. Classic morphology showing dual cell population of epithelial and myoepithelial cells.

The tumor can show necrosis and perineural invasion. There can be foci of lymphovascular invasion, increased mitotic activity and severe nuclear atypia (shown) that can be worrisome for high-grade transformation.

In epithelial myoepithelial carcinoma of parotid gland, p63 stains the myoepithelial cells. CK19 stains the ductal cells.

Images

Webpathology : Epithelial Myoepithelial Carcinoma
http://www.webpathology.com/image.asp?n=18&Case;=968

Epithelial-myoepithelial carcinoma

Epithelial-myoepithelial carcinoma with high grade transformation

https://twitter.com/chioseasi/status/784377089151623169

Microscopy

All tumors show a gradual transition to a high-grade carcinoma from an EMC, each composed of clear cells even in the high-grade regions.

Some cases also show a discrete area with ductal lumina, or plasmacytoid morphology or a squamous differentiation.

It is not possible to separate the high-grade component in these cases into ductal dedifferentiated EMC versus myoepithelial.

Recently, there has been a move to abandon the term "dedifferentiation" in favor of "high-grade transformation" in other salivary gland malignancies.

Synopsis

grossly multinodular
overtly infiltrative
no dedifferentiated areas
low grade tumor
mixed epithelial and myoepithelial components
often multinodular
partial thick fibrous capsule
myoepithelial features with clear cytoplasm or naked nuclei
focal ducts or focal tubules

outer rim of myoepithelial cells and inner
dark ductal cells with scant eosinophilic cytoplasm
round nuclei , bland nuclei

islands, nests or sheets of spindle cells or plasmacytoid (hyaline) cells
mild nuclear pleomorphism
possible high grade transformation / dedifferentiation (Am J Surg Pathol 2010;34:1258)

overt cytologic malignancy
infiltrative growth
perineurial invasion

variable mitotic activity
possible ancient change
possible sebaceous features
posible Verocay-like change

Variants

apocrine variant
dedifferentiated variant
double clear variant
ex pleomorphic adenoma
oncocytic variant (senescence phenotype)
myoepithelial anaplasia variant (myoepithelial overgrowth, Arch Pathol Lab Med 2009;133:950)
dedifferentiated variant

undifferentiated carcinoma of clear cells , spindle cells , squamous cells type
atypia in > 20% cells
no myoepithelial differentiation
older patients
more aggressive behavior
extraglandular and metastastic extension

Immunochemistry

Areas with focal lumina are diffusely positive for CAM5.2 only.

Areas with clear cells show patchy S100 positivity only, whereas cytokeratin 14 and 34betaE12-stained squamous pearls.

Cytology

cellular with single cells and naked nuclei
The biphasic pattern may not be evident since clear cells have fragile cytoplasm and often appear as naked nuclei (Diagn Cytopathol 2003;28:163)

Prognosis

Factors shown to affect behavior include positive margins, vascular invasion, necrosis, and myoepithelial anaplasia.

Differential diagnosis

biphasic salivary gland carcinomas / biphasic salivary tumors

Molecular biology

Frequent morphologic and molecular evidence of preexisting pleomorphic adenoma, common HRAS mutations in PLAG1-intact and HMGA2-intact cases, and occasional TP53 , FBXW7 , and SMARCB1 alterations in high-grade cases. (29135520)

Paywall References

Epithelial-myoepithelial carcinoma with high grade transformation. Roy P, Bullock MJ, Perez-Ordoñez B, Dardick I, Weinreb I. Am J Surg Pathol. 2010 Sep;34(9):1258-65. PMID: 20679885

epithelial-myoepithelial carcinoma

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