Oral Pathology and Oral Medicine
Definitions that get examined
- Leukoplakia: a predominantly white patch that cannot be characterised clinically or pathologically as any other disease and cannot be rubbed off. Subtypes are homogeneous and non-homogeneous (speckled, nodular, verrucous).
- Erythroplakia: a red patch with a higher malignant transformation rate than leukoplakia.
- Dysplasia: architectural changes (drop-shaped rete ridges, loss of polarity, keratinisation) plus cytological atypia (hyperchromatism, pleomorphism, abnormal mitoses). Mild is lower third, moderate middle third, severe upper third; carcinoma in situ is full thickness with an intact basement membrane.
Ulcerative and vesiculobullous disease
- Recurrent aphthous stomatitis: minor, major and herpetiform; begins as an ulcer, not a vesicle; clinical diagnosis.
- Primary herpetic gingivostomatitis: children, vesicles that rupture, tender gingivae; PCR or Tzanck smear; self-limiting.
- Oral lichen planus: bilateral Wickham striae, band-like lymphocytic infiltrate, erosive forms painful; small transformation risk.
- Pemphigus vulgaris: IgG against desmoglein 3, suprabasal acantholysis, flaccid bullae, positive Nikolsky sign, intercellular IgG on direct immunofluorescence.
- Mucous membrane pemphigoid: subepithelial split, linear IgG/C3 along the basement membrane, gingival desquamation, ocular involvement requiring referral.
Cysts and tumours
Radicular cyst is the commonest inflammatory cyst and associates with a non-vital tooth. Dentigerous cyst is the commonest developmental cyst, enclosing the crown of an impacted mandibular third molar. Odontogenic keratocyst shows PTCH1 mutation, satellite cysts and high recurrence. Ameloblastoma favours the posterior mandible with a soap-bubble appearance. Odontoma is the commonest odontogenic tumour-like lesion and is a hamartoma. Among salivary tumours, pleomorphic adenoma is commonest overall and mucoepidermoid carcinoma commonest malignant one.
Worked example
A 58-year-old smoker has a 2 cm indurated, fixed ulcer on the lateral tongue present for 6 weeks with no identified trauma. Reasoning: duration over 3 weeks, induration and fixity are red flags; the working diagnosis is squamous cell carcinoma until biopsy proves otherwise. Action is urgent referral for biopsy and staging imaging, not a review appointment to reassess a presumed traumatic ulcer.
Traps
Labelling every white patch leukoplakia without excluding frictional keratosis, candidiasis or lichen planus; reassuring a patient with an ulcer older than 3 weeks; ignoring that erythroplakia is more dangerous than leukoplakia.