• Clinical science

Diseases of the salivary glands

Abstract

The parotid, submandibular, and sublingual glands are the largest salivary glands. These glands may swell repeatedly and often bilaterally (sialadenosis), but are also subject to acute inflammation that is predominantly unilateral (sialadenitis). Diseases that commonly cause sialadenitis include: Sjögren syndrome (chronic immunologic sialadenitis), Heerfordt syndrome, and mumps (epidemic parotitis). Sialadenosis and sialadenitis primarily affect the parotid gland. However, stones in the salivary ducts (sialolithiasis) mainly form in the submandibular gland because of its ascending salivary duct.

Salivary gland tumors manifest mainly in the parotid. Painless and progressive swelling of the gland is the cardinal symptom of benign as well as malignant tumors, while facial palsy is considered a criterion for malignancy. Generally, the smaller the gland, the greater the chance that the tumor is malignant. Clinical examination and ultrasound play the biggest role in diagnosis. For all parotid tumors, the preferred treatment is parotidectomy with retention of the facial nerve. A resection of the facial nerve is indicated only if it is infiltrated by the tumor. Postoperative radiation therapy may benefit patients with malignant tumors.

Anatomy of salivary glands

In addition to the three larger paired glands – the parotid, submandibular, and sublingual glands – there are several hundred small salivary glands in the oral cavity and throat. As secretory glands, they secrete up to 1.4 L of saliva per day. The primary functions of saliva include:

  • Digestion
  • Protection of the mucosa and teeth
  • Immunological defense
  • Transport of soluble flavors to the taste buds

Parotid gland

  • The parotid gland is located on the surface of the masseter muscle, dorsal to the mandibular branch and ventrocaudal to the external auditory canal in the retromandibular fossa.
  • The facial nerve runs bilaterally through the parotid gland, subdividing into different branches within the gland and separating it into a superficial and a deep lobe.
  • The salivary duct of the parotid gland (Stensen duct) runs forward along the the masseter muscle and opens on the opposite side of the 2nd molar in the oral vestibule (the space between the cheeks and the teeth).
  • The parotid produces mainly serous fluid and approx. 40% of the total amount of saliva.

Submandibular gland

  • Located dorsally in the oral cavity on the mylohyoid and digastric muscles, medial and caudal to the inner surface of the mandible
  • A seromucous gland producing the greater part (approx. 50%) of the secreted saliva
  • The salivary duct (Wharton duct) ends in the sublingual caruncle

Sublingual gland

  • Located in the base of mouth on the mylohyoid muscle and below the sublingual fold
  • The main salivary duct ends in Wharton's duct (salivary duct of the submandibular gland)
  • Produces mainly mucosal secretions

Sialadenosis

References:[1]

Acute purulent sialadenitis

References:[2][3][4]

Sialolithiasis (salivary stones)

  • Location
  • Clinical features: sudden, significant pain while eating; partial swelling of the glands
  • Diagnostics
    • Sonography
    • Sialography (rarely)
    • Possibly x-ray of the skull (particularly the base of mouth)
  • Complications: acute or chronic sialadenitis
  • Treatment: dilatation of the salivary duct or ultrasonic lithotripsy

References:[5][3][4]

Ranula

  • Definition: retention cyst arising in the sublingual gland
  • Epidemiology:
    • Most common between 10-30 years of age, but has been reported in patients aged 3-61 years
    • Rare (∼ 3% of salivary cysts)
  • Etiology: unclear
  • Clinical features
    • Translucent blue swelling below the tongue
    • Can cause problems swallowing and speaking
  • Treatment

References:[6]

Benign tumor

Pleomorphic adenoma

  • Epidemiology
    • Sex: >
    • Peak incidence: 40–60 years
    • Accounts for 85% of benign salivary gland tumors
  • Etiology: ionizing radiation, environmental/occupational exposure (e.g., rubber manufacturing, cosmetologists, nickel compound exposure)
  • Location: mostly the parotid gland (∼ 80% of cases)
  • Clinical features
  • Diagnostics
    • Ultrasound: diagnostic method of choice in salivary gland tumors
    • MRI (T2-weighted image): sharply limited, lobulated hyperintense mass
    • Histology
  • Complications: rarely malignant degeneration (∼ 5% of cases)
  • Treatment: : Best treatment is superficial parotidectomy, to prevent recurrence.
  • Prognosis: very good; recurs in about 5% of cases

Other types of benign salivary gland tumors (monomorphic adenomas)

These benign salivary gland tumors fall under the umbrella term "monomorphic adenoma" because they usually originate in only one type of cell – as opposed to the pleomorphic adenomas, which consist of both epithelial and myoepithelial cells.

Warthin's tumor

  • Epidemiology
    • Sex: >>
    • Peak incidence: 60–80 years
    • 2nd most common benign salivary gland tumor (accounting for 10% of benign cases)
  • Etiology
    • Ionizing radiation
    • Smoking
  • Location: most often the parotid gland
  • Clinical features: gradual and painless unilateral swelling of the parotid
  • Diagnostics
    • Ultrasound: diagnostic method of choice in salivary gland tumors
    • MRI
  • Treatment: complete extirpation of the tumor with preservation of facial nerve
  • Complications: malignant degeneration (rarely)

Rare histologic subtypes

  • Oncocytoma (∼ 2% of cases)
  • Basal cell adenoma (∼ 1–2% of cases)
  • Myoepithelioma (∼ 1% of cases)

References:[5][7][8][9]

Malignant tumor

Malignant salivary gland tumors are referred to collectively because of their many etiological, epidemiological, and pathological similarities.

Submandibular gland tumors are less common but more frequently malignant than parotid tumors. Generally, the smaller the gland, the higher the risk a tumor is malignant!

References:[10][11][12][13][14]

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last updated 08/07/2018
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