Salivary gland tumors exhibit paradoxical behavior:

• Malignancies – indolent
• Benign tumors – aggressive

Incidence:

• Parotid – 65%
• Submandibular glands – 10%
• Sublingual glands < 1%
• Minor salivary glands – 25%

For the intra-oral tumors:

• Palate – 55%
• Upper lip – 20%

Tumorigenesis

Two theories:

1. Bicellular theory: Neoplasms arise from stem cells in excretory and intercalated ducts

• Intercalated ducts:
  • Pleomorphic adenoma
  • Warthin’s tumor
  • Oncocytoma
  • Acinic cell
  • Adenoid cystic
• Excretory ducts:
  • Mucoepidermoid
  • Squamous cell

2. Multicellular theory: Neoplasm develops from various differentiated cells within the salivary gland unit

• Acinar cells: Acinic cell carcinoma
• Intercalated duct: Pleomorphic tumor
• Striated duct: Oncocytic tumor
• Excretory duct:
  • Mucoepidermoid
  • Squamous cell

WHO classification of salivary gland tumors:

1) Adenomas: Benign

• Pleomorphic adenoma
• Monomorphic adenoma: Composed of isomorphic cell population without CT in mixed tumors
  • Basal cell adenoma
  • Myoepithelioma
  • Oncocytoma/ oxyphilic adenoma
  • Warthin tumor (Papillary cystadenolymphoma)
  • Canalicular adenoma
  • Sebaceous adenoma – Rare tumor – sebaceous differentiation of cells – in submandibular and parotid glands
  • Ductal papilloma – Rare tumors – from interlobular and excretory duct portion of the salivary gland unit
• Management: Conservative excision, except basal cell adenoma

2) Carcinomas: Malignant

• Mucoepidermoid carcinomas
• Acinic cell carcinomas
• Adenoid cystic carcinomas
• Carcinoma arising from PSA
• Pleomorphic low grade adenocarcinoma
• Others