Salivary glands
Primary salivary gland neoplasms - benign
Pleomorphic adenoma

Topic Completed: 1 September 2012

Revised: 13 May 2019

Copyright: 2003-2019,, Inc.

PubMed search: Pleomorphic adenoma[TI] salivary glands[TI]

See also: Benign metastasizing mixed tumors

Adriana Handra-Luca, M.D.
Page views in 2018: 48,102
Page views in 2019 to date: 32,187
Cite this page: Handra-Luca A. Pleomorphic adenoma. website. Accessed July 17th, 2019.
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 30s 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
  • 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

Case of the Week #392

External surface

Cut surface

Microscopic (histologic) 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
Microscopic (histologic) images

Contributed by Andrey Bychkov, M.D., Ph.D.

Biphasic population

Case of the Week #404

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

Case of the Week #392

Calcified material

Squamous cells

Eosinophilic globules

Keratinous material

Images hosted on other servers:

Bland epithelial cells and fibrillar, metachromatically staining stroma

Positive stains
Negative stains
Electron microscopy description
  • Features of epithelial and mesenchymal cells
Molecular / cytogenetics description
  • Normal or rearrangements of 8q12 or 12q14-15
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