Oral Pathology and Oral Medicine
What this domain tests
The exam tests whether you can separate a clinical descriptive term from a histological diagnosis, recognise red flags for malignancy, and match immune-mediated diseases to their microscopic level of separation.
Core rules
- Leukoplakia and erythroplakia are clinical diagnoses of exclusion: a white or red patch that cannot be attributed to any other disease. They are not histological diagnoses, and both require biopsy.
- Oral squamous cell carcinoma is the commonest oral malignancy. Red or speckled lesions, induration, fixation, a non-healing ulcer over three weeks, and ipsilateral neck nodes are red flags.
- Dysplasia is graded mild, moderate and severe by architectural and cytological change; severe dysplasia and carcinoma in situ are managed as high-risk lesions.
- Pemphigus vulgaris: IgG against desmoglein 3, suprabasal acantholysis, flaccid blisters, positive Nikolsky sign, direct immunofluorescence with intercellular 'net' pattern.
- Mucous membrane pemphigoid: subepithelial split, linear IgG and C3 along the basement membrane, tense blisters, often gingival.
- Lichen planus: T-cell mediated, white Wickham striae, bilateral buccal, usually painful only in erosive forms.
- Recurrent aphthous stomatitis: minor (<1 cm, heals in 7–10 days), major (>1 cm, scarring), herpetiform (multiple tiny ulcers).
Worked example
A 58-year-old presents with a 2 cm ulcer on the lateral border of the tongue present for six weeks, indurated with everted edges and a fixed submandibular node. Reasoning: chronicity beyond three weeks, induration and nodal fixation point to squamous cell carcinoma. Incisional biopsy of the lesion edge including normal tissue is the correct next step, followed by staging and referral - not a course of antibiotics or a mouthwash.
Traps
Recording 'leukoplakia' as a histopathological diagnosis; treating every ulcer with antifungals or antibiotics; confusing pemphigus (intraepithelial) with pemphigoid (subepithelial) on immunofluorescence; missing that candidal leukoplakia can mimic idiopathic leukoplakia.