Case 231 - Discussion

Uploaded: 2008-05-20, Updated: 2008-05-21

Diagnosis: High-Grade Mucoepidermoid carcinoma

Mucoepidermoid Carcinoma

CLINICAL FEATURES

  • Most common malignant tumor in salivary glands.
  • Most common radiation induced neoplasm of salivary glands.
  • Female predominant, 60.2%. Mean age 47 years.
  • 15.5% of all salivary gland tumor, 29% of all malignant salivary gland tumor, 22% of all malignant tumor in major glands and 41% of all malignant tumors in minor glands.
  • 2/3 occur in parotid gland; also in palate

GROSS FINDINGS

  • May be partially encapsulated with a firm, gray, tan-yellow or pink, and lobulated cut surface.
  • Cysts often seen containing viscid mucoid material.

MICROSCOPIC FINDINGS

  • Variable portions of cords, sheets, clusters of mucous, squamous, intermediate and clear cells;
    • Intermediate cells: outnumber the other cells in most tumors, and they show a transition from small intermediate (basal) to larger intermediate to polygonal and epidermoid cells.
    • Mucinous cells: in small clusters or randomly interspersed among other types of cells. They may resemble intermediate, epidermoid, clear and columnar cells, and they can be large, ovoid or goblet shaped, and have abundant foamy cytoplasm.
    • Epidermoid cells: form small solid nests or partially lined cystic spaces. Rarely keratinized.
    • Clear cells: accounts for about 10% of most cases, but occasionally may be predominant.
  • Characteristically, the tumor often has abundant fibrous stroma that may be hyalinized.
  • Characteristically, many tumors have a predominant cystic or papillary cystic component and small duct-like structures. The cysts are usually lined by mucous, intermediate or epidermoid cells. The lumens are typically filled with mucus.
  • Occasional focal sebaceous cells, oncocytic change, inflammatory reaction to extravasated mucin or keratin and goblet-type cells;
  • Grading:
    • Low grade: numerous cystic spaces formed by various cell types, rare mitoses, bland nuclei;
    • Intermediate grade: often has anaplasia, cystic spaces <20%, may have neural invasion, more mitotic figure and necrosis;
    • High grade: solid and infiltrative growth pattern, anaplasia, >4 mitotic figures/10HPF, more frequent neural invasion, and necrosis.

DIFFERENTIAL DIAGNOSES

  • Poorly differentiated adenocarcinoma

  • Adenosquamous carcinoma with anaplastic nuclear features

  • Necrotizing sialometaplasia

  • Metastatic carcinoma

IMMUNOHISTOCHEMISTRY AND SPECIAL STAINS

  • CK7

  • CK14

  • EMA

  • S100: variable

  • CEA: variable

  • GFAP: variable

  • AFP: stronger in high-grade tumors

CYTOGENETIC STUDIES

  • Associated with t(11;19)(q14-21;p12-13)

TREATMENT AND PROGNOSIS

  • Low grade: 15% recur, 5 year survival 90-98%; usually stage I.

  • High grade: 25% recur, 5 year survival 50-56%; deaths usually within first 5 years.

  • Poor prognostic factors : older age, male, submandibular gland, extraglandular extension, vascular invasion, necrosis, high mitotic rate, high histologic grade.

REFERENCES

  •  AFIP, tumor of the salivary glands, series 3.