General Pathology
General Pathology tests mechanisms of disease that underlie oral and systemic conditions: cell injury, inflammation, repair, hemodynamics, and neoplasia. The exam favors mechanism-based questions and lesion interpretation.
Core rules
- Reversible injury shows swelling and fatty change; irreversible injury shows membrane damage and mitochondrial failure.
- Acute inflammation features vasodilation, increased permeability, and neutrophil emigration; chronic inflammation features lymphocytes, plasma cells, and macrophages.
- Granulomas are collections of activated macrophages; caseating granulomas suggest tuberculosis, while noncaseating granulomas occur in sarcoidosis and Crohn disease.
- Wound healing by primary intention has less granulation tissue and scarring than healing by secondary intention.
- Malignant neoplasms show invasion, metastasis, pleomorphism, and abnormal mitoses.
Worked example
A 60-year-old smoker has painless gross hematuria. Cystoscopy shows a papillary bladder mass. The most likely diagnosis is urothelial carcinoma. Smoking exposes the bladder epithelium to carcinogens concentrated in urine. Painless hematuria is a classic warning sign, and the papillary growth pattern is typical of low-grade urothelial lesions. The reasoning links exposure, site, and clinical presentation rather than relying on a single histologic feature.
Traps
- Metaplasia is a reversible change to another mature cell type; dysplasia is disordered growth and carries risk of progression.
- Benign tumors can be dangerous by location or hormone production.
- Thrombosis forms in flowing blood; embolism travels and lodges elsewhere.
- Caseation is not synonymous with all granulomas.