Epithelial-Myoepithelial Carcinoma of the Salivary Glands

  • Epithelial-myoepithelial carcinoma (EMC):
    • Is another typically indolent salivary gland tumor:
    • That is characterized by a multi-nodular pattern and biphasic or bilayered arrangement of inner ductal cells and outer myoepithelial cells, with classically clear cytoplasm
  • EMC:
  • Is a rare tumor with low malignant potential:
    • Accounting for less than 1 % of salivary neoplasms
  • Peak incidence occurs in seventh decade:
    • With a predilection for female
  • As early as 1956, EMC was reported as:
    • Adenomyoeipthelioma, clear cell adenoma, tubular solid adenoma and clear cell carcinoma:
      • Due to its varied histopathologic appearance
  • The term EMC was coined by Donath et al. in 1972:
    • This discrete entity was subsequently incorporated in WHO classification of salivary gland tumors in 1991
  • On histopathologic examination:
    • It shows dual cell population:
      • Composed of luminal ductal epithelial cells (inner layer) surrounded by large polygonal clear myoepithelial cells (outer layer):
        • Due to bidirectional differentiation of the stem cell
  • The most common location is the parotid gland:
    • Also the index case has parotid involvement:
      • But it is also known to occur in submandibular gland and minor salivary glands of palate, base of tongue and rarely in breast, lung, kidney, uterus
  • Rarely, it may show high grade transformation of epithelial or myoepithelial component:
    • Resulting in aggressive behavior
  • Because of rarity of EMC a standard treatment guideline is not yet known:
    • Surgical resection is the most widely used approach:
      • Although, some of the reported cases have utilized post-operative radiotherapy (PORT) extrapolated from other salivary gland histologies
  • Although it is a low grade tumor:
    • Local recurrence rates of 23% to 50 % have been reported:
      • With 25 % chance of distant metastasis
    • Local recurrence in as early as 6 months post operatively has been seen
  • Histopathologic markers such as:
    • Solid growth pattern, nuclear atypia, DNA aneuploidy, necrosis, positive surgical margins and high proliferative activity:
      • Have been identified by some authors to be associated with more aggressive behavior and high frequency of local recurrences and metastases
  • Surgery alone may not be sufficient in cases with histopathologic markers of aggressive behavior:
    • These patients may be candidates for PORT
CT axial (ab) and coronal (cd) images of face and neck showing enlarged right superficial Parotid gland (awhite arrow) also involving deep lobe of right parotid gland (b black arrow) with small area of necrosis (c white arrowd white arrow)
A well circumscribed tumor with thick fibrous capsule (a HE ×100). There is duct and tubule formation with ducts showing epithelial (broad arrow) and myoepithelial components (line arrow) (b HE ×200). High power view shows a duct composed of an outer rim of myoepithelial cells and inner dark epithelial cells having scant eosinophilic cytoplasm and bland nuclei (c HE ×400). Immunohistochemistry reveals epithelial component staining positively with cytokeratin (d IHC ×400) and SMA staining in the myoepithelial component (e IHC ×400) with MiB-1 labeled cells (f IHC ×400)

#Arrangoiz #CancerSurgeon #HeadandNeckSurgeon #SurgicalOncologist #SalivaryGlandTumors #EpithelialMyoepithelialCarcinoma #EMC #MSMC #MountSinaiMedicalCenter #Mexico #Miami

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