The correct answer is B. The picture shows the classic coagulative necrosis sequela of acute myocardial infarction (MI):
- Most common cause of MI is coronary artery thrombosis.
- Leads to ischemia of dependent tissue and produces coagulative necrosis.
- "Coagulation" necrosis involves denaturation of proteins due to the fall in the pH (lactic acid accumulates as a result of anaerobic metabolism in the absence of sufficient O2) and relative lack of water.
- Cellular architecture and cell outlines are preserved ("ghost cells").
Ischemic damage to most solid organs (except the brain) will produce coagulative necrosis.
Caseating necrosis (choice A) occurs in mycobacterial infection. It develops in the center of granulomas and results from necrosis of epithelioid macrophages, multinucleated giant cells, and mycobacteria. In caseating necrosis, the outlines of cells are entirely lost; and necrotic tissue appears as an amorphous, granular mass, often described as "cheese-like."
Fat necrosis (choice C) is characteristic of acute pancreatitis. It is caused by the release of lipases from the pancreas with resultant autodigestion of peripancreatic and omental fat. It is also seen with trauma to adipose tissue, e.g., breast and thigh. Subsequently, deposition of calcium transforms fatty acids into soaps (saponification), which become apparent as chalky-white areas.
Fibrinoid necrosis (choice D) occurs in inflammatory processes involving arteries (vasculitis) and malignant hypertension. Necrosis of the media and intima, with effacement of their structural components, is associated with deposition of plasma proteins and appears pink on histologic sections, which appear morphologically similar to fibrin (hence the designation).
Liquefactive necrosis (choice E) results in "liquefaction," due to the digestion of proteins by hydrolases released by microorganisms and/or neutrophils. Liquefactive necrosis usually occurs in association with infection, abscesses, and cerebral infarcts.
This is a multi-step question.
What is the question asking?
You are being asked to identify the type of necrosis that is present in the specimen shown on the image.
What is the first step?
The first step is to identify relevant information in the question vignette that may help us make a diagnosis.
- This patient was a 70-year-old male who initially presented with chest pain and diaphoresis.
- Ultimately the patient died in the ICU as a result of ventricular fibrillation.
Although it is not clear that the patient was having a MI, it can be inferred based on the history of chest pain associated with diaphoresis. Ventricular fibrillation, along with other arrhythmias, can present during the post-MI period and lead to sudden cardiac death. An autopsy was done and a cross-sectional slice of the heart shows an infarct, which appears as an area of pale discoloration that is well demarcated with preserved tissue architecture. The cardiac specimen provided in the image confirms the diagnosis of MI.
What is the next step?
Next, we must determine which type of necrosis is seen in MI. Coagulative necrosis (choice B) occurs in most cases of solid-organ ischemia, including MI. Acidosis in ischemic tissue leads to protein denaturation, which deactivates proteolytic enzymes and preserves tissue architecture around the area of necrosis. Coagulative necrosis is firm in texture, well-demarcated, and paler compared with surrounding normal tissue.
Can other answers be eliminated?
The other answer choices can be eliminated because they are not a type of necrosis seen in MI:
- Caseating necrosis (choice A) is usually associated with tuberculosis infection and certain fungal infections.
- Fat necrosis (choice C) is seen in pancreatic autodigestion.
- Fibrinoid necrosis (choice D) is typically associated with vasculitis and malignant hypertension.
- Liquefactive necrosis (choice E) is most commonly seen in bacterial infections and brain ischemia.
What is the single best answer and why?
Coagulative necrosis (choice B) is the single best answer because it is the usual type of necrosis seen in MI and in most other solid organs. Ischemia and acidosis result in protein denaturation and loss of proteolysis, leading to the preservation of tissue architecture despite necrosis. Areas of necrosis are firm in texture, well-demarcated, and pale in color.
MedEssentials (4th Ed.): pp. 155
First Aid (2019): pp. 209.1
First Aid (2018): pp. 209.1
First Aid (2017): pp. 205.1
Pathoma (2018-2019): pp. 73.1, 74.1 Table, 75.1 Image
Pathoma (2014-2017): pp. 73.1, 74 Table, 75 Image
