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epithelial-myoepithelial carcinoma

Thursday 2 September 2010

EMC; EMCA

WKP PO WP

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

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

- 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-OrdoƱez B, Dardick I, Weinreb I. Am J Surg Pathol. 2010 Sep;34(9):1258-65. PMID: 20679885