Salivary Gland Neoplasms

Salivary gland tumours comprise a significant proportion of oral tumours and are the next most common neoplasms of the mouth after SCC.


Epidemiology

(90% rule) 90% of salivary gland tumours occur in the parotid gland. 90% are benign. 90% are pleomorphic salivary adenomas (PSA’s.)

The next most common salivary gland tumour is carcinoma.  Submandibular gland tumours are usually PSA’s, malignant tumours 33% in SM gland.  Sublingual tumours are very rare and mostly malignant.

50% of minor salivary gland tumours are malignant. PSA’s are the most common neoplasm.  They mostly arise in the palate.

The incidence of salivary gland cancers in Europe is estimated at 1.2 per 100 000.

 

Aetiology

Little is known as to the aetiology of salivary gland tumours except that they can result from irradiation to the head area. Survivors of Hiroshima and Nagasaki have shown excess salivary gland tumours. Similarly, therapeutic irradiation can have similar effects.  There is also a correlation between salivary gland and breast cancer.

 

Classification

Classified by the World Health Organisation into epithelial tumours, non-epithelial tumours and unclassified tumours.

 

Epithelial tumours

1. Adenomas

  • Pleomorphic adenoma (mixed, rubbery, recurs if excision inadequate-poorly encapsulated)
  • Monomorphic adenomas (adenolymphoma-Warthin’s, 10% of parotid tumours, benign)

 

2. Carcinomas

  • Mucoepidermoid carcinoma (10% of salivary tumours, slow-growing, benign)
  • Acinic cell carcinoma (v.rare, usually benign)
  • Adenoid cystic carcinoma (slow-growing, malignant with tendency to infiltrate, spread perineurally)
  • Adenocaricinoma

 

3. Epidermoid carcinoma

  • Undifferentiated carcinoma
  • Carcinoma in pleomorphic adenoma

 

4. Non-epithelial tumours

  • Lymphomas (predisposed to if have Sjogren’s syndrome)
  • Sarcomas

 

Symptoms

Usually benign tumours present as a painless, slow-growing swelling that the patient may be aware of for several years. Cystic tumours may be fluctuant. Facial nerve palsy, pain and ulceration may be seen with parotid mucoepidermoid and acinic cell carcinomas.  Classic eversion of ear lobe in Parotid gland neoplasms.

 

Signs

A soft rubbery unilateral swelling which may feel lobulated in benign tumours. Malignant tumours tend to grow faster, are of hard consistency and may ulcerate and invade bone.

 

Diagnostic tests

  • Fine needle aspiration (+/- ultrasound guided) to obtain a sample of tissue for microscopic examination of the cells.  There is a risk of tumour cells being seeded in the needle track.
  • Ultrasound
  • Computerized tomography (CT scan) 
  • Magnetic resonance imaging (MRI scan –useful to delineate lesion)
  • Sialography is useful for chronic inflammatory changes, filling defects, or gland displacement but is of little value in diagnosing tumours

 

Management

Early detection carries a good prognosis.

With the exception of lymphomas, the treatment of choice is surgical excision, patient permitting. Principles are complete excision of tumour with margin of healthy tissue and preservation of facial nerve. In possibly malignant tumours, frozen sections may help to decide whether facial nerve can be preserved. Radiotherapy is often combined with surgery in cases of malignant tumours.