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PH-GI11

Salivary gland tumours

How the two-layered duct system of the salivary glands gives rise to benign tumours such as pleomorphic adenoma and Warthin tumour and to carcinomas, why a smaller gland means a higher chance of malignancy, and what facial weakness signals.

By the end, you can

  • Describe the secretory unit of a salivary gland and the luminal and myoepithelial cells that most tumours resemble.
  • Compare pleomorphic adenoma and Warthin tumour: their cells, gross and microscopic appearance, and behaviour.
  • Describe the main salivary carcinomas, including mucoepidermoid and adenoid cystic carcinoma, and how each spreads.
  • Explain why the proportion of malignant tumours rises as the gland gets smaller.
  • Relate facial weakness, pain, fixation and enlarged neck nodes to invasion and spread.
  • Recognise the classic appearances, site rules, staging and tests of salivary tumours, and explain how parotidectomy that protects the facial nerve, neck dissection and radiotherapy act on their growth and spread.

What it is

A salivary gland tumour is a neoplasm of the major (parotid, submandibular or sublingual) or minor salivary glands. Most arise from the cells lining the ducts and from the myoepithelial cells around them, so many copy the two-layered pattern of the normal duct. Most parotid tumours are benign, the commonest being pleomorphic adenoma; the commonest carcinomas are mucoepidermoid and adenoid cystic carcinoma.

5 types to tell apart
Pleomorphic adenoma
The commonest salivary tumour: duct and myoepithelial cells in a myxoid, cartilage-like stroma inside an incomplete capsule. Benign, but it regrows if left behind and can rarely turn malignant after many years.
Warthin tumour
Cysts and papillae lined by a double layer of oncocytic (mitochondria-rich) cells over dense lymphoid tissue; almost confined to the parotid, linked to smoking, sometimes on both sides.
Mucoepidermoid carcinoma
The commonest salivary carcinoma: mucous, squamoid (epidermoid) and intermediate cells; graded low, intermediate or high, which predicts its behaviour.
Adenoid cystic carcinoma
Duct and myoepithelial cells in sieve-like (cribriform) nests; grows slowly but spreads along nerves and can reach the lungs years later.
Carcinoma ex pleomorphic adenoma
A carcinoma arising within a pleomorphic adenoma, usually one present for many years or one that has recurred.

US spelling: tumours → tumors, tumour → tumor.

Normal function

Glands built from acini and two-layered ducts

Saliva comes from three pairs of major glands and hundreds of minor glands in the lining of the mouth and throat. The , the largest, lies in front of the ear over the ramus of the mandible and makes watery (serous) saliva, which drains through the . The make mixed serous and mucous saliva; the and the minor glands make mostly mucus.

Each gland is a branching tree. Secretory acini pour saliva into narrow intercalated ducts, then striated ducts that adjust its salt content, then larger excretory ducts. Acini and intercalated ducts have two cell layers: inner luminal (acinar or duct) cells and outer, contractile myoepithelial cells that squeeze saliva onwards, with basal reserve cells that renew them.

Two features of the parotid matter for its tumours. The facial nerve runs through it, splitting the gland into superficial and deep parts as it branches to the muscles of facial expression. And lymph nodes lie on and inside the gland, draining to the nodes of the neck.

Point to it on the model