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Case 94 - Discussion

Surgical Pathology Case

Pleomorphic Adenoma (Mixed Tumor)

DEFINITION

 
  • Benign salivary gland tumor compose of ductal epithelial and myoepithelial proliferation within a mesenchymal background.

CLINICAL FEATURES

 
  • Most common tumor of the salivary glands, 54-76%; most common in parotid glands;

  • Peak in 40-50 year-old, F>M;

  • Slowing growing, asymptomatic, mobile;

GROSS FINDINGS

 
  • Round-oval, well-circumscribed, variably encapsulated mass;

  • Cut surface, homogeneously white-tan shiny, partly translucent zones;

  • Recurrent tumors often show multiple separated nodules in the normal salivary glands.

MICROSCOPIC FINDINGS

 
  • Fibrous capsule: variable thickness,  may contain small finger-like extensions or islands of neoplastic cells;

  • Epithelial cells types: spindle, clear, squamous, basaloid, cuboidal, plasmacytoid, oncytoid, stellate, mucous, and sebaceous. May form glandular, ductal or tubular patterns;

  • Mesenchymal stroma: myxoid, mucochondroid, hyalinized, osseous, and/fatty.

SUBTYPES

 
  • Cellular type

  • Myxoid type

DIFFERENTIAL DIAGNOSES

 
  • Chondroid syringoma

IMMUNOHISTOCHEMISTRY AND SPECIAL STAINS

 
  • Cytokeratin cocktail, positive in ductal epithelium and myoepithelium;

  • Myoepithelium: positive for vimentin, S100, GFAP, SMA

TREATMENT AND PROGNOSIS

 
  • 20-45% recurrence rate, risk of malignant transformation.