Oral and Maxillofacial Pathology
The pathology section asks you to convert a clinical and radiographic picture into a recognised diagnosis and then name the microscopic or molecular feature that confirms it. Questions concentrate on cyst-versus-tumour logic, frequency data, and the relationship between a lesion and a tooth.
Cyst and tumour framework
- Radicular cyst: the most common jaw cyst; always inflammatory, always on a non-vital tooth; cholesterol clefts and Rushton bodies.
- Dentigerous cyst: attaches at the cementoenamel junction and encloses the crown of an unerupted tooth.
- Odontogenic keratocyst: parakeratinised lining, palisaded basal cells, PTCH1 mutation; multiple keratocysts in Gorlin syndrome with basal cell carcinomas, bifid ribs and a calcified falx.
- Ameloblastoma: BRAF V600E, posterior mandible, third to fifth decade, locally aggressive; unicystic variants with mural invasion behave differently.
- Odontoma: the most common odontogenic tumour overall, a hamartoma, compound or complex.
Mucosa and salivary glands
- Squamous cell carcinoma is the most common oral malignancy; lateral tongue and lower lip dominate; erythroplakia and proliferative verrucous leukoplakia carry the highest transformation risk.
- Pleomorphic adenoma is the most common salivary neoplasm; mucoepidermoid carcinoma is the most common malignant one.
- Pemphigus vulgaris shows suprabasal acantholysis with intercellular IgG; mucous membrane pemphigoid shows subepithelial separation with linear IgG and C3 at the basement membrane.
Worked example
A 34-year-old has a 3 cm multilocular radiolucency at the mandibular angle with scalloped margins and a displaced impacted third molar, and no paraesthesia. Multilocularity with a displaced tooth in this age group points first to ameloblastoma, then keratocyst, then odontogenic myxoma. A keratocyst grows anteroposteriorly with little expansion; a myxoma often shows fine septa. Management starts with incisional biopsy, then resection for solid ameloblastoma.
Marks-losing traps
Exchanging the most-common labels; calling a lesion dentigerous when the cyst attaches at the cementoenamel junction; forgetting that a radicular cyst requires a dead tooth.