Case 87 - Discussion

Uploaded: 2007-08-31, Updated: 2007-10-02

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.