General Pathology
General Pathology tests cell injury and adaptation, inflammation and repair, hemodynamics, neoplasia, and immunopathology. Questions ask you to classify a process, distinguish reversible from irreversible change, or identify the most likely mechanism.
Core rules
- Adaptations: hypertrophy increases cell size; hyperplasia increases cell number; atrophy decreases size; metaplasia replaces one mature cell type with another; dysplasia is disordered growth with atypia.
- Reversible injury shows swelling and fatty change; irreversible injury shows membrane failure, mitochondrial damage, and nuclear changes such as pyknosis, karyolysis, and karyorrhexis.
- Acute inflammation features vasodilation, increased permeability, and neutrophil emigration; chronic inflammation features lymphocytes, plasma cells, and macrophages.
- Granulomas are collections of activated macrophages, seen in tuberculosis and foreign-body reactions.
- Benign tumors are well circumscribed, non-invasive, and do not metastasize; malignant tumors invade and metastasize.
- Oncogenes are activated gain-of-function genes; tumor suppressors require loss of function.
Worked example
A biopsy from an enlarged prostate shows more glands with normal architecture and no atypia. The cell number is increased but the cells are normal, so the process is hyperplasia, not hypertrophy or dysplasia. If the same tissue showed crowded glands with nuclear enlargement and loss of polarity, dysplasia would be the better description, and carcinoma in situ would be considered if the basement membrane were intact but the full thickness were atypical.
Traps
- Metaplasia is an adaptation, not cancer, though it may raise cancer risk.
- Dysplasia can be reversible; it is not synonymous with malignancy.
- A benign tumor can still cause serious harm by location or hormone secretion.