Pathology (general and oral)
Pathology: what is tested
This domain combines general pathology mechanisms with oral and maxillofacial lesions. The exam favors diagnosis from mechanism, behavior, and microscopic pattern.
Core rules
- Coagulative necrosis follows ischemia; caseous necrosis is typical of tuberculosis; liquefactive necrosis occurs in brain and abscesses.
- Acute inflammation features vasodilation, increased permeability, and neutrophil influx; chronic inflammation features macrophages, lymphocytes, and fibrosis.
- Neoplasia: dysplasia implies disordered maturation; carcinoma in situ has full-thickness atypia without invasion.
- p53 is a tumor suppressor; RAS and MYC are oncogenes; HPV16 is linked to oropharyngeal squamous carcinoma.
- Radicular cyst arises from epithelial rests of Malassez after pulp necrosis; it is lined by nonkeratinized stratified squamous epithelium with inflammation.
- Odontogenic keratocyst has a parakeratinized lining, palisaded basal layer, and high recurrence; it is associated with PTCH1.
- Ameloblastoma is locally aggressive, often posterior mandible, and frequently has BRAF V600E.
- Pleomorphic adenoma is the most common salivary tumor; mucoepidermoid carcinoma is linked to MAML2 translocation.
- Oral epithelial dysplasia and erythroplakia carry higher malignant transformation risk than homogeneous leukoplakia.
Worked example
A nonvital maxillary incisor has a periapical radiolucency. Reasoning: pulp necrosis leads to periapical inflammation, then proliferation of Malassez rests and cyst formation. The expected diagnosis is radicular cyst, lined by nonkeratinized stratified squamous epithelium with chronic inflammation. A dentigerous cyst instead surrounds the crown of an impacted tooth and attaches at the cementoenamel junction.
Traps
- Calling all periapical radiolucencies cysts; granulomas are common.
- Confusing odontogenic keratocyst with dentigerous cyst.
- Forgetting that erythroplakia has higher transformation risk than leukoplakia.
- Staging versus grading: stage is extent, grade is differentiation.