Pleomorphic adenoma

Pleomorphic adenoma 

Updated: 02/13/2021

© Jun Wang, MD, PhD

General features

• AKA Benign mixed tumor
• Most common tumor of salivary glands
• Most common in parotid gland
• More common in women
• Risk factors for malignant transformation: submandibular location, older age, larger size, radiation exposure

Pathogenesis

• Unclear etiology
• Prior radiation increases risk
  
• Probably associated with Simian virus (SV40)

Clinical features

• Painless, slow growing tumor
• Usually NOT involving facial nerve
• Rapid growth if malignant transformation (carcinoma ex pleomorphic adenoma)

Pathological features

• Single firm, mobile, well-circumscribed mass
• Triphasic population of benign ductal cells, myoepithelial cells and stromal cells
• Fibrous capsule
• Ductal and myoepithelial components: Commonly glandular, may be squamous, spindled or oval, myoepithelial cells as the outer layer
  
• Mesenchymal components: Various, may be myxoid, hyaline, chondroid, adipose or osseous; mucin often present

Genetic abnormality

• PLAG1 rearrangement

Management

• Surgery
• Recurrence uncommon
• May have malignant transformation (carcinoma ex pleomorphic adenoma)

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