Mucoepidermoid carcinoma (MEC)

  • Mucoepidermoid carcinoma (MEC):
    • Is the most common malignant neoplasm of the:
      • Mayor and minor salivary glands
  • Epidemiology:
    • They encompass between 2.8% to 15.5% of all salivary gland tumors
    • Among 12% to 35% of malignant salivary gland tumors
    • Among 6.5% to 41% of all minor salivary gland tumors:
      • Representing the most common type of malignant minor salivary gland tumor in most series
    • Approximately half the cases occur in the major salivary glands:
      • 65% to 80% of these occur in the parotid
      • 8% to 13% occur in the submandibular gland
      • 2% to 4% involve the sublingual gland
    • MEC of the minor salivary glands:
      • Ordinarily arises on the palate:
        • But a number may also be found in the:
          • Retro molar area
          • Floor of the mouth
          • Buccal mucosa
          • Lip
          • Tongue
    • Its prevalence is highest in:
      • The fourth to fifth decade of life (35 to 65 years of age):
        • With a female preponderance as high as 4:1
  • Grossly:
    • The tumor is poorly circumscribed and measures from 3 to 5 cm
  • Histologically:
    • They are characterized by a mixed population of cells, including:
      • Mucin-producing cells
      • Epidermoid cells with squamoid differentiation
      • Clear cells
      • Intermediate cells:
        • That may predominate in numbers
        • Are believed to be the progenitor of the other types of cells
      • No myoepithelial cells are present
  • The clinical behavior of MEC has proved to be difficult to predict:
    • But correlations to tumor grade and stage have been reported
    • The histologic features that are most useful in predicting the aggressive nature of these tumors are:
      • A minor cystic component (less than 20%)
      • Tumor necrosis
      • Neural invasion
      • Cellular anaplasia
      • Brisk mitotic activity
    • Based on the presence or absence of these features and the clinical behavior, MEC are classified as:
      • Low grade
      • Intermediate grade
      • High grade
    • Low-grade MEC are:
      • Well circumscribed, with pushing margins and dilated cystic areas containing mucin
      • Mucin producing, intermediate, or epidermoid cells make up the lining of these cystic structures
    • Intermediate-grade MEC:
      • As the grade worsens:
        • The tumors become more infiltrative, poorly circumscribed
        • Cystic formations are lost
        • Nests of tumor become more solid and irregular with intermediate or epidermoid cells dominating
    • High-grade MEC are characterized by:
      • The invasion of adjacent structures
      • Atypical mitoses
      • Necrosis
      • Perineural invasion
      • Lymph node metastasis:
        • 40% to 50%
      • Distant metastases
    • Differential diagnosis of these high-grade lesions are:
      • Primary of metastatic squamous cell carcinoma:
        • MEC is differentiated from metastatic SCC by:
          • The presence of intracellular mucin
      • Sebaceous carcinomas
      • Clear cell carcinomas
  • Histologic grade and tumor stage:
    • Appear to have profound effects on survival
    • Aro et al:
      • Found a statistically significant difference in disease free survival (DFS) by grade:
        • Between low-grade MEC and intermediate / high-grade MEC (P = 0.001)

#Arrangoiz #CancerSurgeon #HeadandNeckSurgeon #SurgicalOncologist #SalivaryGlandCancer #MucoepidermoidCarcinoma #ParotidTumors #MEC #CASO #CenterforAdvancedSurgicalOncology #Miami

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