Diseases of the salivary glands

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.

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 ramus and ventrocaudal to the external auditory canal in the retromandibular fossa.
• The facial nerve runs through the parotid gland, subdividing into different branches within the gland
• The salivary duct of the parotid gland (Stensen duct) runs forward along the masseter muscle and opens adjacent to the 2^nd molar in the vestibule of the mouth (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 also ends in the Wharton duct (salivary duct of the submandibular gland)
• Produces mainly mucous secretions

• Definition: acute inflammation of the salivary glands
• Etiology
  • Pathogens: usually bacterial (commonly Staphylococcus aureus, Streptococcus viridans, Haemophilus Influenzae, Streptococcus pyogenes, Escherichia Coli; rarely viruses such as mumps and HIV)
  • Risk factors
    • Cachexia in intensive care patients
    • Postoperatively (due to dehydration, intubation)
    • Intensive teeth cleaning
    • Decreased salivation (due to fasting, special diet)
    • Immunodeficiency
    • Salivary stones
    • Advanced age
    • Anticholinergic drug use
    • Oral neoplasia
    • Malnutrition
• Location: most often the parotid gland
• Clinical features
  • Acute onset
  • Unilateral painful swelling and erythema overlying the salivary gland
  • Usually with purulent discharge expressed from duct orifice
  • Systemic toxicity: fever, chills
• Diagnostics
  • Mostly a clinical diagnosis
  • ↑ Serum amylase indicates parotid involvement
  • Gram stain and culture of discharge
  • Ultrasound or CT if abscess is suspected
• Treatment
  • Hydration
  • Stimulation of salivation (chewing gum, lemon drops)
  • Intravenous antibiotics: nafcillin + metronidazole OR clindamycin
    • Immunocompromised patients: vancomycin OR linezolid + one of the following:
      • Cefepime + metronidazole
      • Imipenem
      • Meropenem
      • Piperacillin-tazobactamPoor response to 48 hours of antibiotics or an abscess: surgical drainage and decompression
  • Recurrent infections: parotidectomy
• Complications: deep neck infections

References:^[2][3][4]

• Location
  • Primarily in the submandibular gland (∼ 80% of cases)
  • Parotid gland (∼ 20% of cases)
• Clinical features: acute, significant pain while eating; partial swelling of the glands
• Diagnostics
  • Sonography
  • Noncontrast CT
  • 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]

• 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
  • Extirpation of the ranula, including the sublingual gland
  • Marsupialization

References:^[6]

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
  • Gradual and painless unilateral swelling of the parotid gland
  • Robust, movable tumor
• Diagnostics
  • Ultrasound: diagnostic method of choice in salivary gland tumors
  • MRI (T2-weighted image): sharply limited, lobulated hyperintense mass
  • Histology
    • Mixed cellular constitution with myoepithelial cells and chondroid tissue
    • Cytokeratin is expressed immunohistochemically
• Complications: rarely malignant transformation (∼ 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
  • 2^nd 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: rarely malignant transformation

Rare histologic subtypes

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

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

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

• Location: parotid gland → parotid carcinoma
  • Less common locations
    • Submandibular and sublingual carcinomas
    • Carcinomas of the salivary glands in the gums and the base of the mouth
• Etiology
  • Ionizing radiation
  • Viral infection (e.g., HIV or HPV may be implicated )
• Symptoms
  • Insidious onset
  • Painless submucosal swelling or mucosal ulceration (palate, buccal mucosa, lips)
  • In some cases, clinical symptoms arise if the neighboring structures are infiltrated (e.g., facial palsy caused by parotid carcinomas).
• Diagnostics
  • Ultrasound of the head and neck (to determine location and size of mass); with or without biopsy (definitive diagnosis)
  • Contrast enhanced CT/MRI of head and neck: useful as preoperative workup to determine location, size, and extension of the lesion
• Pathology
  • Subtypes
    • Mucoepidermoid carcinoma
      • Most common malignant salivary gland tumor in children
      • Involves both epidermal and mucosal cells
    • Adenoid cystic carcinoma (obsolete term: cylindroma)
      • Growth along nerve sheaths
      • Cribriform or tubular growth pattern
      • Very slow, but dangerous infiltrative growth
    • Acinic cell carcinoma
    • Adenocarcinoma
    • Metastases of other malignant tumors in head and neck
  • Routes of metastasis
    • Initially lymphogenic in local lymph nodes
    • Later hematogenic metastasis, particularly in the lungs
• Treatment
  • Curative
    • Parotidectomy (superficial or total), if possible, with preservation of the facial nerve
    • +/- Neck dissection and/or adjuvant radiotherapy for extensive or higher grade tumors
  • Palliative: chemotherapy
• Complications of a parotidectomy
  • Facial nerve injury (most common early complication)
  • Hematoma
  • Salivary fistula
  • Frey syndrome: gustatory sweating
  • Crocodile tears (gustatory hyperlacrimation): Regenerating parasympathetic gustatory fibers attach to the lacrimal gland.

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]}