Oral Biology, Oral Pathology and Oral Medicine
Oral pathology and oral medicine: vignettes describing a white patch, an ulcer, a swelling or a radiograph, followed by the most likely diagnosis, the next investigation, or the underlying mechanism. This domain rewards pattern recognition of red flags more than long differential lists.
Core rules
- Any oral ulcer persisting beyond 2–3 weeks, or an indurated lesion on the lateral tongue, floor of mouth or retromolar region, requires incisional biopsy - not a therapeutic trial of antibiotics, antifungal or steroid.
- Leukoplakia is a clinical diagnosis of exclusion; erythroplakia carries the higher malignant transformation risk. Dysplasia is a histological diagnosis, not a clinical one.
- Pemphigus vulgaris: IgG against desmoglein 3, suprabasal acantholysis, flaccid blisters, positive Nikolsky sign, intercellular 'chicken-wire' IgG on direct immunofluorescence.
- Mucous membrane pemphigoid: subepithelial split with linear IgG/C3 at the basement membrane; desquamative gingivitis is typical.
- Reticular oral lichen planus shows bilateral Wickham striae on the buccal mucosa; manage with topical corticosteroid and review, because a small transformation risk exists.
- Radiolucencies: radicular cyst at a non-vital apex, dentigerous cyst around the crown of an unerupted tooth, keratocyst (locally aggressive, high recurrence), ameloblastoma (multilocular, posterior mandible, root resorption).
Worked example
A 58-year-old tobacco chewer has a 5-week indurated ulcer on the left lateral tongue and a hard, fixed submandibular node. Duration exceeds the 2–3 week threshold, the site is classic, and induration with a fixed node suggests malignancy with nodal involvement. The next step is an incisional biopsy of the lesion edge plus neck imaging and referral to oral and maxillofacial surgery - not an antifungal trial, and not excisional biopsy before a tissue diagnosis.
Traps
- Labelling a unilateral indurated ulcer in an older patient as 'aphthous'.
- Calling every radiolucency a cyst; keratocyst and ameloblastoma are tumours.
- Discharging a patient with a white patch after antifungal treatment without review.
- Assuming a normal radiograph excludes malignancy - soft-tissue lesions may need no imaging before biopsy.