Which histopathological feature best distinguishes acute pulmonary embolism from acute myocardial infarction in a patient presenting with sudden chest pain and death?

Explanation

## Histopathological Distinction Between PE and AMI ### Key Diagnostic Feature **Key Point:** Acute pulmonary embolism is characterized by the presence of a fibrin thrombus (often with platelets and red blood cells) lodged within pulmonary arteries, which is the pathognomonic finding that distinguishes it from myocardial infarction. ### Comparative Pathology | Feature | Acute PE | Acute MI | |---------|----------|----------| | **Primary lesion** | Fibrin thrombus in pulmonary arteries | Coagulation necrosis of myocardium | | **Location** | Pulmonary arterial tree | Left ventricular wall | | **Morphology** | Laminated thrombus with platelets, fibrin, RBCs | Ischemic necrosis with wavy fibers at margins | | **Timeline** | Thrombus present from onset | Necrosis develops over 4–12 hours | | **Associated findings** | Pulmonary infarction (rare, only if bronchial circulation compromised) | Contraction band necrosis, coagulation necrosis | ### Why This Matters **High-Yield:** The fibrin thrombus within pulmonary arteries is the **direct anatomical cause** of PE and is immediately visible on histology, whereas myocardial necrosis is a secondary consequence of ischemia and develops over time. This makes the thrombus the gold-standard discriminator. **Clinical Pearl:** In sudden cardiac death from PE, autopsy reveals the thrombus in situ; in sudden cardiac death from AMI, the coronary artery may show atherosclerosis and plaque rupture, but the myocardial necrosis is still developing or absent if death occurs within the first few hours. [cite:Robbins 10e Ch 4]