Oral Medicine, Oral Pathology, and Oral Diagnosis
Core concepts
Candidates must be able to move from a lesion's clinical description to a defensible differential. Learn the vocabulary of description first: site, size, shape, colour, surface, border, consistency, duration, and behaviour over time. Then link morphology to mechanism - ulceration (traumatic, aphthous, infective, malignant), white lesions (keratosis, candidiasis, lichen planus, leukoplakia), red lesions (erythroplakia, atrophic candidiasis, erosive lichen planus), and pigmentation (amalgam tattoo, melanotic macule, melanoma).
Oral potentially malignant disorders deserve special attention. Leukoplakia is a diagnosis of exclusion - a white patch that cannot be attributed to any other cause. The trap is labelling every white patch leukoplakia; questions often give a frictional keratosis on the buccal mucosa at the occlusal line, which resolves with removal of the cause. Non-homogeneous (speckled) leukoplakia carries higher transformation risk than homogeneous. Erythroplakia has the highest malignant transformation of the clinical white/red group.
Diagnostic reasoning
A systematic history (SOCRATES-style pain analysis, medical history, drugs, habits) followed by examination and appropriate investigation is the expected sequence. Incisional biopsy of the most suspicious area is the rule for large lesions; excisional biopsy suits small, accessible lesions. Fine-needle aspiration is for neck lumps, not intraoral mucosal lesions.
Traps
- Confusing recurrent aphthous stomatitis with herpes simplex: aphthae are non-keratinised mucosa only, no vesicles, and are not infective.
- Missing medication-related causes: ulceration from nicorandil, gingival overgrowth from calcium channel blockers, lichenoid reactions from gold or amalgam.
- Forgetting that oral candidiasis can be the first sign of undiagnosed diabetes or immunosuppression.
Worked example
A 58-year-old smoker has a 2 cm non-healing ulcer on the lateral tongue of six weeks' duration, indurated with rolled margins. Rule of thumb: any oral ulcer persisting beyond two to three weeks without a clear cause requires referral and biopsy to exclude squamous cell carcinoma. Do not prescribe a topical steroid and review - that is the classic wrong answer.