Necrotizing Sialometaplasia

Necrotizing sialometaplasia is a benign, self-limiting inflammatory lesion of minor salivary glands, most often on the posterior hard palate, characterised by ischaemic necrosis of glandular lobules and squamous metaplasia of the ducts and acini. Its importance lies in its clinical and histological resemblance to squamous cell and mucoepidermoid carcinoma, which can lead to misdiagnosis and unnecessary radical surgery. It is rare, with a male to female ratio of 2 to 1 and peak age 40 to 60 years.

The cause is local vascular compromise:

• trauma (dental injections, intubation, denture trauma, surgery, bulimia and vomiting)
• local anaesthetic injection with vasoconstrictor
• smoking, cocaine use
• upper respiratory infection
• radiotherapy
• sickle cell disease or other vascular disease

Infarction of the gland lobules triggers necrosis and regenerative squamous metaplasia (pseudoepitheliomatous hyperplasia).

The condition heals spontaneously within 4 to 10 weeks with no recurrence, and no specific treatment is needed. The lesion is benign and does not become malignant.

• Deep, crater like ulcer 1 to 4 cm in diameter, with a rolled or erythematous border, on one side of the posterior hard palate (75 percent), near the junction with the soft palate; bilateral or midline in 10 percent.
• Initially a swelling, with pain, paraesthesia or numbness, followed by ulceration within 2 to 3 weeks; the ulcer may expose bone.
• Occasionally other sites: soft palate, lip, retromolar pad, tongue, parotid, nasal cavity, larynx.
• Usually painless or mild discomfort; no lymphadenopathy.
• Red flags: hard fixed mass, lymphadenopathy, rapid growth, bone destruction, persistent beyond 10 weeks, haemoptysis, or constitutional symptoms (exclude carcinoma, lymphoma and infection).

• History of preceding swelling and trauma; clinical appearance of a crater ulcer on the posterior hard palate.
• Incisional biopsy including adjacent normal tissue, essential before any surgical treatment: lobular necrosis of acini with preserved lobular architecture, intact mucin, squamous metaplasia of ducts and acini with nests of squamous cells (which mimic carcinoma but lack nuclear atypia and invasion), pseudoepitheliomatous hyperplasia of the surface epithelium, and an inflammatory infiltrate.
• Review of pathology by an experienced head and neck pathologist; immunohistochemistry (p63 positive in both, but a low Ki-67 index and absent atypia favour the benign lesion).
• CT or MRI if bone erosion, deep extension, or malignancy is suspected.
• Culture, serology (syphilis, deep fungal tests, tuberculosis) for ulcers that do not heal.
• Exclude squamous cell carcinoma, mucoepidermoid carcinoma, minor salivary gland carcinoma, lymphoma, deep fungal infection, tuberculosis, syphilitic gumma, granulomatosis with polyangiitis, and traumatic ulcer.

• Reassurance and watchful waiting after a diagnostic biopsy: spontaneous healing occurs by secondary intention over 4 to 10 weeks.
• Local care: warm saline mouthwash (half a teaspoon of salt in a cup of warm water) after meals, 4 to 6 times daily; chlorhexidine gluconate 0.2 percent mouthwash 10 mL twice daily for 7 to 14 days to reduce secondary infection.
• Analgesia: paracetamol 1 g orally every 6 hours; benzydamine 0.15 percent rinse 15 mL every 3 hours as needed; topical lidocaine 2 percent viscous 5 mL before meals.
• Protection: a palatal splint or denture adjustment to prevent trauma; soft, non-acidic diet.
• Antibiotics only for secondary infection: amoxicillin 500 mg orally every 8 hours for 5 to 7 days.
• No surgery or radiotherapy is indicated once the diagnosis is confirmed.
• Remove contributing factors: stop smoking and cocaine use; avoid further trauma.
• Follow up: review at 2 weeks and 6 to 8 weeks until healed; repeat biopsy when the ulcer persists beyond 10 weeks.
• Counselling: the condition is not cancer, it heals alone, and re-biopsy occurs if healing stalls.