1.4 Differential Diagnosis, Triage & When to Biopsy
Key Takeaways
- Triage separates presentations that threaten the airway, circulation or a cancer diagnosis from those that can safely wait: airway compromise, spreading infection with systemic upset, uncontrolled bleeding, avulsed permanent teeth and suspected malignancy all take priority
- An unexplained oral ulcer, red patch, white patch or lump persisting beyond three weeks triggers an urgent suspected-cancer referral under NICE NG12
- Incisional biopsy samples a representative area including the lesion edge and adjacent normal tissue and is used for large or suspected malignant lesions; excisional biopsy removes the whole lesion with a margin and suits small, clinically benign lesions
- Biopsy of a suspected oral squamous cell carcinoma belongs in the head and neck cancer service, not in general dental practice, because it forms part of staging and surgical planning
- Recognising missing information is itself a syllabus outcome — an incomplete medical history, an untested pulp or an unmeasured mouth opening should stop the plan rather than be assumed
Building a Differential Diagnosis
Outcome B2.8 asks candidates to construct an appropriate differential diagnosis from the information provided, examination and investigations. A workable method is to generate categories before generating names, using a surgical sieve adapted for the mouth:
| Category | Examples in the oral cavity |
|---|---|
| Developmental | Cysts of developmental origin, tori, dental anomalies |
| Infective | Odontogenic abscess, herpetic gingivostomatitis, candidiasis, syphilis, tuberculosis |
| Inflammatory / immune | Lichen planus, pemphigoid, pemphigus, recurrent aphthous stomatitis, orofacial granulomatosis |
| Traumatic | Frictional keratosis, traumatic ulcer, denture hyperplasia, mucocele |
| Neoplastic | Squamous cell carcinoma, salivary neoplasms, lymphoma, metastases |
| Metabolic / endocrine | Brown tumour of hyperparathyroidism, diabetic periodontal breakdown |
| Iatrogenic / drug | Lichenoid reaction, gingival overgrowth, MRONJ, osteoradionecrosis |
| Idiopathic | Burning mouth syndrome, geographic tongue |
Then rank by probability and by consequence: the most likely diagnosis and the most dangerous diagnosis both belong in the differential, because the plan must exclude the dangerous one.
Recognising missing information (outcome B3.3)
Outcome B3.3 is explicit that a clinician must recognise when important information is missing and take appropriate action. In SBA stems the missing item is usually one of: an un-updated medical history, an anticoagulant with no recent INR, an untested pulp in a tooth about to be extracted, an unmeasured mouth opening in a spreading infection, no radiograph before an extraction, or no record of what the patient was told. The correct answer is almost always to obtain the missing information rather than to proceed.
Triage: Urgent Versus Non-Urgent (Outcome B2.7)
| Priority | Presentation | Action |
|---|---|---|
| Immediate (999 / same-hour) | Airway compromise, Ludwig's angina, stridor, anaphylaxis, uncontrolled haemorrhage, suspected facial fracture with airway or eye signs, avulsed permanent tooth | Emergency management and immediate referral |
| Same-day | Spreading odontogenic infection with systemic upset, trismus or dysphagia; post-extraction bleeding not controlled by pressure; acute dento-alveolar trauma; dental abscess with fever | Urgent assessment, drainage, escalation as needed |
| Within two weeks | Unexplained ulceration, red or white patch, or lump persisting more than three weeks; unexplained tooth mobility; persistent unilateral neck lump | NICE NG12 suspected-cancer pathway referral |
| Routine urgent | Irreversible pulpitis, pericoronitis, localised abscess, fractured restoration causing trauma | Emergency dental appointment |
| Routine | Asymptomatic caries, replacement restorations, elective prosthodontics | Planned care |
The most examined discriminators are airway (dysphagia, drooling, muffled voice, raised floor of mouth, trismus, stridor), systemic upset (fever, tachycardia, malaise, rigors) and persistence beyond three weeks for mucosal lesions.
Soft-Tissue Swelling (Outcome B3.7)
When assessing a swelling, record site, size, shape, surface, consistency, colour, temperature, tenderness, fluctuance, pulsatility, mobility and duration, plus whether it crosses the midline and whether it varies with meals.
| Feature | Points towards |
|---|---|
| Fluctuant, tender, warm, rapid onset, related to a non-vital tooth | Odontogenic abscess |
| Firm, non-tender, slow growing, in the parotid tail | Pleomorphic adenoma |
| Bluish, fluctuant, on the lower lip in a young patient | Mucocele |
| Swelling at mealtimes, resolving between meals | Salivary obstruction |
| Diffuse, firm, bilateral, raising the floor of mouth | Ludwig's angina — airway emergency |
| Hard, fixed, painless, with an ulcerated surface | Malignancy |
| Bilateral, painless, parotid | Sialosis, Sjögren's, drug effect, alcohol-related |
When to Submit Tissue for Pathological Examination (Outcome B2.10)
Tissue should be submitted whenever the diagnosis cannot be made clinically with confidence, whenever a lesion is a potentially malignant disorder, and whenever a lesion has been removed. Specific triggers:
- Any unexplained ulcer or mucosal lesion persisting beyond three weeks.
- Any white or red patch that cannot be wiped off and cannot be attributed to a definite local cause.
- Any lesion that is enlarging, indurated, fixed or ulcerating.
- Every excised specimen, including apparently trivial ones — an apparent fibroepithelial polyp is occasionally something else.
- Cyst linings and bone lesions removed at surgery.
Incisional versus excisional biopsy (outcome C3.2)
| Technique | Indication | Practical points |
|---|---|---|
| Incisional | Large lesions, suspected malignancy, diffuse mucosal disease | Sample the most representative area, include the lesion edge with adjacent normal tissue, avoid necrotic centre; take more than one sample from a heterogeneous lesion |
| Excisional | Small (roughly under 1 cm), clinically benign, well-defined lesions | Remove the whole lesion with a narrow margin; for a mucocele, remove the associated minor gland or it recurs |
| Punch | Flat mucosal lesions, immunobullous disease | Quick and reproducible; for direct immunofluorescence take perilesional, not ulcerated, tissue and send it fresh or in Michel's medium, not formalin |
| Fine needle aspiration cytology | Neck lumps and salivary masses | First-line for a parotid mass; avoids the seeding risk of open biopsy |
Practical rules that carry marks: infiltrate local anaesthetic around rather than into the lesion; handle the specimen with a suture rather than crushing it with forceps; orientate it for the pathologist; fix in 10% neutral buffered formalin at about ten times the specimen volume; and complete the request form with the clinical description, differential and relevant history.
Where the biopsy happens matters. A lesion suspicious of oral squamous cell carcinoma should be referred on the suspected-cancer pathway rather than biopsied in general dental practice: the biopsy forms part of staging and surgical planning, and an ill-placed primary-care incision can distort the surgical field and delay definitive care.
A 58-year-old smoker has a 12 mm indurated ulcer on the floor of the mouth present for six weeks. What is the most appropriate action in general dental practice?
A patient is booked for extraction of a lower molar. The medical history form was completed 18 months ago, the patient now mentions 'a heart problem' and new tablets she cannot name, and no radiograph has been taken. What does syllabus outcome B3.3 require?
A biopsy is being taken from perilesional mucosa in a patient with suspected mucous membrane pemphigoid, for direct immunofluorescence. How should the specimen be handled?
Which combination of findings in a patient with facial swelling most urgently indicates a threat to the airway?