Salivary glands
Epithelial / myoepithelial tumors
Pleomorphic adenoma

Authors: Adriana Handra-Luca, M.D. (see Authors page)

Revised: 15 June 2016, last major update September 2012

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PubMed search: pleomorphic adenoma salivary gland

Related topics: Benign metastasizing mixed tumors
Definition / General
  • Most common tumor of salivary glands
  • Painless, slow growing tumor, composed of biphasic population of epithelial and mesenchymal cells
  • Also called benign mixed tumor
Clinical Features
  • Often women in 30’s, but any age
  • 90% occur in parotid gland (represent 60% of parotid tumors; 50% occur in tail, 25% in superficial lobe, 25% in deep lobe), 10% in submandibular gland, rare in sublingual gland
  • Represents 50% of salivary gland tumors of palate
  • Epithelial and mesenchymal (myxoid, hyaline, chondroid, osseous) cells often arise from same cell clone (Hum Pathol 2000;31:498), which may be a myoepithelial or ductal reserve cell
  • No difference in behavior based on proportion of various elements
  • Risk factors for malignant transformation: submandibular location, older age, larger size, prominent hyalinization, increased mitotic rate (if present, sample tumor more thoroughly), radiation exposure
Case Reports
Treatment
  • Wide local excision (25% recur with enucleation, 4% with adequate parotidectomy)
  • Recurrences are usually within 18 months, but can be up to 50 years later (Arch Pathol Lab Med 2008;132:1445)
  • After surgery for recurrent tumor, 25% recur again
Gross Description
  • Well-demarcated, partially encapsulated, gray-white, myxoid, rubbery mass with solid cut surface, often 6 cm or less, tumor extensions into adjacent tissue may be subtle
Gross Images

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Case of the Week #392:

External surface

Cut surface



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White tumor with myxoid cut surface

Micro Description
  • Not as well circumscribed as may grossly appear, with tongue like protrusions into surrounding salivary gland
  • Thick capsule if present in deep parotid lobe
  • Biphasic population of epithelial and mesenchymal cells
  • Epithelial cells are glandular or occasionally squamous; may be spindled or oval, have large hyperchromatic nuclei
  • Myoepithelial basal layer or overlying pseudoepitheliomatous hyperplasia; tumor may be very cellular
  • Stroma is myxoid, hyaline, chondroid, rarely adipose tissue or osseous; mucin often present
  • Occasional angiolymphatic invasion
  • May have adenoid cystic pattern
  • No mitotic figures, no necrosis
Micro Images

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Case of the Week #392:

Squamous metaplasia

Keratin granuloma

Conventional area

Adipocytic metaplasia

Keratinous cyst with lamellar keratin

Cytology Description
  • Clusters of benign epithelial cells with blue myxoid matrix and tyrosine-rich crystals
Cytology Images

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Case of the Week #392:



Calcified material

Squamous cells

Eosinophilic globules

Keratinous material



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Bland epithelial cells and fibrillar, metachromatically staining stroma

Positive Stains
  • Ductal component: CK19, CK14, EMA, CEA, alpha-1-antitrypsin, alpha-1-antichymotrypsin, GCDFP-15, PSA (50%), PAP (50%)
  • Myoepithelial component: keratin, actin, myosin, other smooth muscle proteins, S100 (particularly in cartilaginous areas), GFAP
Negative Stains
  • Amylase, p53
Molecular / Cytogenetics Description
  • Normal or rearrangements of 8q12 or 12q14-15
Electron Microscopy Description
  • Features of epithelial and mesenchymal cells