Definition

Salivary gland tumours are growths found in the salivary glands. The salivary glands include:

  • Major (paired)
    • Parotid glands
    • Submandibular glands
    • Sublingual glands
  • Minor
    • 600-1000 found beneath the mucosa of oral cavity and oropharynx.

 

These tumours can be benign or malignant, with parotid tumours less likely to be malignant than those in the submandibular, sublingual or minor salivary glands.

 

Epidemiology

Salivary gland tumours have an incidence of 1 in 100,000. They are slightly more common in women than in men and more common in adults. Tumours found in children are more likely to be malignant.

Malignant tumours of the salivary glands are rare. In the UK, malignant salivary gland tumours are responsible for 1 in every 100 cancers that are diagnosed.

Origin of salivary gland cancers:

  • 80% in the parotid glands
  • 10% in submandibular glands
  • 10% in the sublingual and minor glands

 

Aetiology

Mainly idiopathic

Risk factors:

  • Previous exposure to radiation
  • Age (50s and 60s)
  • Previous squamous cell carcinoma
  • Human Papilloma Virus
  • Smoking

 

Pathophysiology

Benign tumours:

  • Pleomorphic adenomas
  • Warthin’s Tumour

Tumours of variable malignancy :

  • Mucoepidermoid tumours
  • Acinic cell carcinoma

Malignant tumours :

  • Adenoid cystic carcinoma
  • Adenocarcinoma
  • Carcinoma ex-PSA
  • Low grade polymorphous cancers
  • Lymphoma
  • Squamous cell carcinoma (rare)
  • Lymphoepithelioma (rare)
  • Anaplastic carcinoma (rare)
  • Metastatic tumours from elsewhere

Pleomorphic adenoma

These are the most common tumours of the salivary gland. They usually arise in the parotid gland and are derived from intercalated duct reserve cells. They are benign but have the potential to become malignant if left for many years (see Carcinoma ex-PSA). All the tumour cells most be removed during surgery to avoid recurrences.

Warthin’s Tumour

Warthin’s Tumour is also known as adenolymphoma, it is not, however, a type of lymphoma. It usually arises in the parotid gland, commonly the tail. It is more common in men (8:1) and occurs in older people. It may feel soft and cystic.

Mucoepidermoid tumour

These tumours can either be low-grade (well-differentiated) or high-grade (poorly differentiated). The better differentiated they are, the more slowly they grow and the more likely they are to be painless. Both tumour types will need resecting, but high-grade tumours will also require radiotherapy. They are derived from the epithelial cells of interlobar and intralobular ducts and are usually found in the parotid gland. They are more common in women than in men and are the most common type of salivary gland tumour in children.

Acinic cell carcinoma

This is a slow-growing tumour which develops in the acinar cells and is usually found in the parotid gland. It is more common in females.

Adenoid cystic carcinoma

This is the most common malignant tumour of the salivary glands. It grows slowly and spreads locally, but the long-term prognosis is poor. Recurrence is common and distant metastases can occur. It can infiltrate the nerves, causing pain and nerve palsies. It is derived from reserve epithelial cells of the intercalated ducts and can occur in any of the major or minor glands.

Adenocarcinoma

These develop in the epithelial cells of any of the major or minor salivary glands. They are rare but highly malignant and have a poor prognosis.

Carcinoma ex-PSA

These can develop from a benign pleomorphic adenoma, usually years later.

Low grade polymorphous cancers

These are rare and usually occur in the over-70s. They are seen in the minor salivary glands and grow slowly.

Lymphoma

These are non-epithelial tumours and are usually Non-Hodgkin’s Lymphoma.

 

Signs and symptoms

  • A swelling in the face/neck which may be slow-growing (benign or low-grade) or rapidly-growing (malignant)
  • If painless: more likely to be benign
  • Facial palsy or nerve palsy: more likely to be malignant
  • Lymph nose metastases may be felt on examination

Investigations

  • Fine-needle aspiration
  • Ultrasound/CT/MRI scan
  • Chest X-ray (for another primary and/or metastases)
  • Excisional biopsy (NB avoid incisional biopsy as seeding can occur, leading to recurrence)

Treatment

  • Excision of benign tumours
  • Malignant tumours require wide local excision and may need radiotherapy and excision of affected lymph nodes

Complications

Complications include neural involvement, causing pain and nerve palsies.

Complications of surgery:

  • Facial nerve palsy
  • Haematoma
  • Salivary fistula (usually resolves with time)
  • Frey’s Syndrome (the skin over the area of the parotid bed sweats when eating)

 

References

Corbridge RJ. Essential ENT. 2nd ed. London: Hodder Arnold; 2011

Ellis H, Calne R, Watson C. Lecture Notes: General Surgery. 12th ed. Chichester: Wiley-Blackwell; 2011

Munir N, Clarke R. Ear, Nose and Throat at a Glance. Chichester: Wiley-Blackwell; 2013

Nottingham School of Medicine Specials Handbook

www.macmillan.org.uk

www.cancerresearchuk.org

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