Pathology and Pathophysiology
Core concepts
Pathology questions connect mechanism to morphology. Know the core processes: inflammation (acute versus chronic, granulomas), cell injury and death (necrosis types - coagulative, caseating, fat, liquefactive - versus apoptosis), neoplasia (benign versus malignant, carcinoma versus sarcoma, tumor markers, staging versus grading), hemodynamics (thrombosis, embolism, infarction, edema), and the major organ system pathologies (atherosclerosis, cirrhosis, nephrotic and nephritic glomerular disease, emphysema versus chronic bronchitis). Understand the cell cycle and the difference between hypertrophy, hyperplasia, metaplasia, and dysplasia.
Traps
The most common trap is confusing mechanism with appearance: caseating granulomas suggest tuberculosis, noncaseating granulomas suggest sarcoidosis, but both are granulomatous inflammation. Another is mixing up metaplasia (reversible change of one mature cell type to another, e.g., Barrett esophagus) with dysplasia (premalignant disordered growth). Questions may test whether a marker is for screening, prognosis, or monitoring - and whether staging (spread) differs from grading (differentiation). Also distinguish transudate from exudate by protein content and cells, and know that infarction morphology depends on the organ's dual blood supply.
Worked rule of thumb
For any pathology stem, run a four-step chain: etiology, mechanism, morphologic change, clinical consequence. Example: chronic gastroesophageal reflux leads to squamous-to-columnar metaplasia (Barrett esophagus), which predisposes to dysplasia and adenocarcinoma. That chain lets you answer both "what is the finding" and "what is the next step" (surveillance endoscopy). When a stem gives a histologic description, name the process (inflammation, neoplasia, degeneration) before choosing the diagnosis.