Salivary Gland Diseases: Sialadenitis to Tumours Overview

The salivary glands (parotid, submandibular, and sublingual pairs, plus hundreds of minor glands) produce about a litre of saliva a day for digestion, taste, speech, and tooth protection. Their diseases fall into three groups: inflammation (sialadenitis), stones (sialolithiasis), and tumours, benign and malignant.

This matters because symptoms are distinctive: pain and swelling that flare while eating points to a stone blocking the duct, while a painless slow-growing lump in front of the ear points to a tumour. Mixing them up delays the right treatment.

Key Concepts

• Sialadenitis: gland infection. Bacterial (often Staphylococcus aureus) follows dehydration; viral is classically mumps (paramyxovirus) in unvaccinated children.
• Sialolithiasis: salivary stones, mostly in the submandibular gland, whose long Wharton's duct carries saliva uphill against gravity, letting minerals settle.
• Pleomorphic adenoma: the most common salivary tumour ("mixed tumour"); a slow painless lump, usually in the lower pole of the parotid. Microscopic outpouchings through its capsule mean simple enucleation recurs: the correct operation is superficial parotidectomy.
• Mucoepidermoid carcinoma: the most common malignant salivary tumour; low-grade behaves well, high-grade spreads aggressively.
• Adenoid cystic carcinoma: notorious for perineural spread along nerves (pain or numbness) and late distant metastasis; its cribriform pattern looks like Swiss cheese microscopically.
• Warthin's tumour: benign, almost exclusive to the parotid, strongly linked to smoking, sometimes bilateral.

Formulas

Saliva flow is measured, and the numbers define dry mouth:

• Normal unstimulated whole saliva: about 0.3 to 0.4 mL per minute.
• Hyposalivation: below 0.1 mL per minute, needing active management.
• The test: the patient spits all saliva into a graduated cup for 5 minutes; volume divided by 5 gives the rate. Example: 1.5 mL in 5 minutes = 0.3 mL/min, which is normal.

Worked Example

A 52-year-old woman on multiple medicines complains of constant dry mouth. Unstimulated collection yields 0.4 mL in 5 minutes.

1. Flow rate = 0.4 / 5 = 0.08 mL/min.
2. Below the 0.1 mL/min threshold: confirmed hyposalivation, likely medicine-induced.
3. Management: review medicines with her physician, high-fluoride toothpaste (dry mouths decay fast), saliva substitutes, and sugar-free gum to stimulate flow.

Common Misconceptions

• "Every parotid lump is cancer." Most are benign, pleomorphic adenoma leading; but every lump still needs imaging and usually fine-needle aspiration.
• "Stones only form in kidneys." Salivary stones are common, especially submandibular, causing the classic mealtime swelling.
• "Dry mouth is just old age." Medicines are the leading cause; reviewing the drug list often finds the culprit.

Real-World Applications

• ENT and oral surgeons remove stones (increasingly by sialendoscopy) and perform parotidectomy while preserving the facial nerve.
• Dentists manage xerostomia with fluoride regimens, saliva substitutes, and caries prevention.
• Radiologists use ultrasound as first-line imaging for salivary lumps and stones.

Salivary disease sorts by symptom: mealtime pain and swelling means a stone, most likely submandibular; a painless slow parotid lump is most likely pleomorphic adenoma needing formal parotidectomy; dry mouth is measurable, with 0.1 mL per minute as the line between complaint and disease. Image the lump, measure the flow, protect the facial nerve.