Pleomorphic Adenoma

 

Common sites:

    • Parotid > Submandibular
    • Buccal cavity

 

Gross features:

    • rounded, well-demarcated
    • rarely >6cm
    • encapsulated
    • cut surface gray-white with myxoid and blue translucent areas (chondroid)

 

Histologic features:

    • heterogeneity
    • 2 cell populations:
      • ducts, acini, irregular tubules, strands, or sheets
      • myoepithelial cells in strands or sheets
        • cleared cytoplasm often
        • spindled, plasmacytoid appearances
      • epithelial cells lining ducts
        • regular cuboidal lining
        • more eosinophilic cytoplasm
      • may have islands of well-differentiated squamous epithelium
      • usually no dysplasia
      • usually no mitoses
    • mesenchyme-like background:
      • loose myxoid tissue
      • islands of chondroid
      • rarely foci of bone
    • rule out carcinoma ex pleomorphic adenoma
      • adenocarcinoma or undifferentiated carcinoma
      • look especially in fibrous areas
      • look for presence or absence of myoepithelial cells around atypical ducts / nests

 

Immunophenotype:

Marker:

Sensitivity:

Specificity:

Stains for epithelial component:

EMA

CK7

GFAP

PAS (mucin in glands)

 

 

Stains for myoepithelial component:

S100

P63

Calponin

SMA

CK7 (weaker)

 

 

PAS (mucin within glands)

 

 

c-kit (neg)

usually

 

 

Molecular features:

    •  

 

Other features:

    •