Salivary Gland Tumors

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Basics

Salivary gland tumors consist of benign or malignant neoplasms of the major and minor salivary glands. Tumors may be mimicked clinically by a variety of inflammatory or infectious disorders:

  • Major: parotid, submaxillary, sublingual glands
  • Minor: intraoral, pharyngeal, and nasal glands (600 to 1,000 glands distributed throughout the upper aerodigestive tract)

Description

  • Adult neoplasms
    • Benign: pleomorphic adenoma, Warthin tumor (adenolymphoma), oncocytoma, and monomorphic adenoma
    • Malignant: mucoepidermoid carcinoma, adenoid cystic carcinoma, acinic cell carcinoma, carcinoma ex pleomorphic adenoma, squamous cell carcinoma (SCC), adenocarcinoma
  • Total distribution of salivary gland neoplasms by type
    • Pleomorphic adenoma (most common): 45% overall
    • Monomorphic adenoma: 12% overall
    • Mucoepidermoid carcinoma: 12% overall
    • Adenoid cystic carcinoma: 6% overall
    • Remaining neoplasms: 25% overall
  • Distribution: parotid (80%); submandibular (10–15%); sublingual and minor (5–10%)
    • Parotid (80% benign; 20% malignant)
      • Pleomorphic adenoma: 60%
      • Monomorphic adenoma: 8%
      • Warthin tumor: 8%
      • Mucoepidermoid carcinoma: 12%
      • Adenoid cystic carcinoma: 5%
      • Adenocarcinoma and SCC: 5%
    • Submandibular (60% benign; 40% malignant)
      • Pleomorphic adenoma: 40%
      • Mucoepidermoid carcinoma: 10%
      • Adenoid cystic carcinoma: 20%
    • Lingual and minor salivary glands (40% benign; 60% malignant)
      • Pleomorphic adenoma: 40%
      • Mucoepidermoid carcinoma: 25%
      • Adenoid cystic carcinoma: 25%; generally, as the size of the gland decreases, the incidence of malignancy increases.
  • Pediatric neoplasms
    • These tumors are most frequently benign but may be malignant.
    • Benign: 65% of overall cases; the most common types are hemangiomas (before age 1 year) and pleomorphic adenomas (>1 year old). Warthin tumor, lymphoepithelioma, myoepithelioma, and basal cell adenoma can also occur (1)[B].
    • Malignant: 35% of overall cases; most common type is mucoepidermoid carcinoma. Other types seen include acinic cell carcinoma, adenoid cystic carcinoma, and sialoblastoma (1)[B].

Epidemiology

Incidence
  • 1.5/100,000 cases in individuals in the United States
  • ~700 deaths annually
  • Median age
    • Benign: 45 years
    • Malignant: 60 years
  • Gender predilection
    • Benign: female > male
    • Malignant: male = female

Prevalence
Make up 6–8% of all head and neck neoplasms (2)[A]

Etiology and Pathophysiology

Etiology and pathophysiology not fully understood; certain pathways and oncogenes have been implicated: p53, Bcl-2, PI3K/Akt, MDM2, VEGF, HGF, and ras.

  • Predominant/bicellular theory: Tumors arise from either the secretory duct reserve cell or the intercalated duct reserve cell.
  • Multicellular theory: Tumors arise from several cell types of origin within the salivary gland unit.

Genetics
Increased incidence of adenocarcinoma of parotid in Eskimos; otherwise, no known genetic pattern

Risk Factors

  • Tobacco and alcohol abuse associated with Warthin tumor
  • Alcohol increases likelihood ratio by 2:1.
  • Radiation has shown a 4-fold increased dose-related response in salivary gland cancer 15 to 20 years after treatment. Increased risk has also been reported in atomic bomb survivors.
  • EBV has been associated with lymphoepithelial carcinoma in Asians, but there is no evidence of causal association in other tumors.
  • Silica dust has been associated with a 2.5-fold increase in salivary gland neoplasia.
  • Kerosene-cooking fuel exposure
  • Nitrosamine exposure in rubber workers
  • Early menarche and nulliparity

General Prevention

Cessation of tobacco and alcohol use

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