Oral Pathology and Oral Medicine
This domain tests recognition and safe triage of mucosal, salivary, osseous and odontogenic disease: which white or red lesion needs biopsy now, which ulcer is immune-mediated, and which jaw radiolucency is a cyst, a tumour or something harmless.
White and red lesions
The decisive question is whether a lesion can be rubbed off (candidiasis, materia alba) and whether it is homogeneous or non-homogeneous. Leukoplakia is a diagnosis of exclusion - a persistent white patch that cannot be attributed to another cause. Non-homogeneous leukoplakia and erythroplakia carry the highest malignant transformation risk; erythroplakia is the highest of the two.
Ulceration and vesiculobullous disease
- Recurrent aphthous stomatitis: round, shallow, grey-based, no keratinisation, heals in 7–14 days.
- Herpes simplex: grouped vesicles on keratinised mucosa, multinucleated giant cells and viral inclusion bodies on cytology.
- Pemphigus vulgaris: intraepithelial, suprabasal acantholysis, IgG against desmoglein 1 and 3, positive Nikolsky sign, fragile bullae.
- Mucous membrane pemphigoid: subepithelial split, linear IgG and C3 along the basement membrane, intact tense bullae, gingival desquamation common.
- Oral lichen planus: bilateral white striae, band-like lymphocytic infiltrate, saw-tooth rete ridges; low but real malignant potential.
Tumours and cysts
Squamous cell carcinoma accounts for over 90% of oral malignancy; lateral tongue, floor of mouth and retromolar region predominate. Ameloblastoma is the commonest clinically significant odontogenic tumour (soap-bubble radiolucency, resorption of roots); odontogenic keratocyst is locally aggressive and linked to PTCH1. Among salivary tumours, pleomorphic adenoma is commonest overall and mucoepidermoid carcinoma commonest malignant one; adenoid cystic carcinoma is notorious for perineural spread.
Worked example
A 58-year-old smoker has a 3 cm indurated ulcer on the lateral tongue present for six weeks, fixed to underlying tissue, with a firm ipsilateral submandibular node. Reasoning: any ulcer over three weeks without an identifiable cause is suspicious; induration plus fixation plus a hard node makes carcinoma the working diagnosis. The correct action is urgent referral for incisional biopsy and staging imaging - not antifungal or antibiotic trials with review.
Traps that cost marks
- Calling a white patch leukoplakia without excluding frictional keratosis, candidiasis and lichen planus.
- Treating a persistent ulcer empirically and delaying referral - the single commonest clinical error in this domain.
- Missing that the floor of mouth and ventral tongue are the highest-risk sites.