Salivary gland tumours
- Topic
Most salivary tumours are in the parotid and are benign. The smaller the gland, the more likely a tumour is malignant.
What it is
Salivary gland tumours are uncommon but varied, with more than 30 types. Most arise in the parotid and most parotid tumours are benign, while tumours of the submandibular, sublingual and minor glands are more often malignant. Clinical features cannot reliably tell benign from malignant, so biopsy or resection decides. Mucoepidermoid carcinoma is the commonest malignancy; adenoid cystic carcinoma invades nerves; acinic cell carcinoma copies serous acini.
Structure
- Mucoepidermoid: unencapsulated, grey-white, with mucin cysts; cords, sheets and cysts of squamous, mucous and intermediate cells.
- Adenoid cystic: small dark cells in cribriform, tubular or solid nests around hyaline or basophilic material; tumour wrapping nerves.
- Acinic cell: sheets, microcysts and follicles of cells resembling serous acinar cells with purple granular cytoplasm (PAS positive, diastase resistant).
- High-grade change: pleomorphism, mitoses and necrosis in any type.
Step by step
- Salivary tumours arise from ductal, myoepithelial or acinar cells (or their reserve stem cells).
- Characteristic fusion genes drive several types: CRTC1::MAML2 in mucoepidermoid, MYB::NFIB in adenoid cystic.
- Radiation exposure and, for Warthin tumour, smoking raise risk.
- Adenoid cystic carcinoma spreads along nerve sheaths, explaining pain, facial palsy and positive margins.
- Long-standing benign mixed tumours accumulate changes and can transform into carcinoma.
Salivary tumours to know
| Tumour | Behaviour | Usual site | Key histology | Gene |
|---|---|---|---|---|
| Pleomorphic adenoma | Benign (commonest overall) | Parotid | Epithelium, myoepithelium, chondromyxoid stroma | PLAG1, HMGA2 |
| Warthin tumour | Benign | Parotid only | Oncocytic bilayer over lymphoid stroma | None defining |
| Mucoepidermoid carcinoma | Malignant (commonest) | Parotid, minor glands | Squamoid, mucous, intermediate cells | CRTC1::MAML2 |
| Adenoid cystic carcinoma | Malignant | Minor glands (palate) | Cribriform, perineural invasion | MYB::NFIB |
| Acinic cell carcinoma | Malignant, usually low grade | Parotid | Serous acinar-like cells with granules | NR4A3 |
Markers
- PLAG1
- MAML2
- MYB
- NR4A3
- PAS (zymogen granules)
Clinical notes
- A painless mass in front of or below the ear is usually benign; pain or facial weakness changes the picture.
- Low-grade mucoepidermoid carcinoma rarely metastasises; high-grade tumours recur and metastasise often.
- Adenoid cystic carcinoma has good five-year but poor long-term survival because of late recurrences.
Test yourself
Think of the answer, then tap the question to see it.
How does gland size relate to the risk that a salivary tumour is malignant?
Inversely: most parotid tumours are benign, whereas a larger share of submandibular, minor and sublingual gland tumours are malignant.
What is the most common malignant salivary gland tumour and its typical fusion gene?
Mucoepidermoid carcinoma, often with a CRTC1::MAML2 fusion from t(11;19).
Why does adenoid cystic carcinoma often recur and cause pain?
It invades along nerves (perineural invasion), making complete excision difficult; recurrences can appear many years later.
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Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Parotid Cancer (StatPearls (NCBI Bookshelf), 2025); Salivary Gland Disorders (MedlinePlus, US National Library of Medicine, 2025).
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Representative model, for educational purposes only.