Salivary Gland Tumours

• Parotid most common site for almost all tumours; 60% of parotid gland masses are benign

• Tumours in smaller glands are more likely to be malignant

Benign tumours

Pleomorphic adenoma

• Most common tumour

• Usually females, 3-6th decade in parotid with a long history

• Pathogenesis unknown, but there is a known link with radiation

• Risk of malignant transformation if longstanding

• Macroscopic apearance - well circumscribed, light tan to grey

• Microscopic appearance - highly variable epithelial and myoepithelial cells in chondromyxoid stroma

Warthin's tumour

• Second most common benign tumour

• Usually males over 50

• Rare outwith the parotid

• Strong association with smoking

• Often bilateral and multicentric

• Macroscopic - well circumscribed, light grey, cystic

• Microscopic - bilayered oncocytic epithelium with lymphoid stroma

Malignant tumours

• If young and a painful mass, think malignancy

Mucoepidermoid carcinoma

• Most common malignant salivary gland tumour worldwide

• Majority in parotid, but can occur in any gland

• Wide age range, no sex predominance

• Classified into high or low grade
• Low grade - > 90% 5 year survival
• High grade - < 60% survival

• Associated with MECT1-MAML2 fusion

• Macroscopic - can be well circumscribed or infiltrative

• Microscopic - variable mix of squamous, mucous and intermediate cells, with solid and cystic components

Adenoid cystic carcinoma

• Most common in the UK

• Wide age range and range of sites

• Usually over 40 and in parotid but also the most common malignant tumour of the palate

• 50-70% 10-year survival

• Frequent perineural invasion - associated pain or loss of function

• Macroscopic -greyish/white infiltrative mass

• Microscopic - small, uniform cells with little cytoplasm in solid, tubular or cribiform plate

Clinical presentation

• Mass in the affected gland which may or may not have been present for a long time

• Signs of CN VII (facial nerve) damage e.g. facial nerve palsy are associated with malignant parotid tumours

Investigations

• US

• FNA

• Staging
• CT - local relations
• MRI - deep lobe of parotid, relations with CN VII

Management

• Salivary gland tumours are nearly always resected e.g. superficial or total parotidectomy
• Usually in their early stages it is not possible to distinguish a benign tumour from a malignant one
• There is a risk of malignant transformation of adenoma if left alone

• Facial nerve, retromandibular vein and external carotid artery are at risk during a parotidectomy