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Questions
- Definition
- Etiopathogenesis
- Morphological variants
- Clinical Implications
Introduction
- Definition– Necrosis is a form of localised cell injury which results in the premature death of living tissue by autolysis followed by degradation by hydrolytic enzymes liberated from dead cells. It is always pathological and causes inflammation.
- Classical Findings of Necrosis-
- Inflammation
- Pathological pain
- Leaking out of intracellular components such as Trop I.
Pathophysiology
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- Oncosis (cellular and organellar swelling)
- Mitochondrial and ER swell up
- ATP not produced
- Ribosomes released into cytoplasm
- RNA lost
- Nuclear changes such as Pyknosis, Karyorrhexis and karyolysis take place
- Autolysis
Coagulative Necrosis
- Most common pattern of necrosis
- Caused by ischemic injury resulting from hypoxic death of cells
- Solid organ infarct
- Occurs in all tissues except brain
- Plasma membrane is damaged but not dissolved completely, hence cell outline is maintained for a few days
- Neutrophils are visible
- Highly eosinophilic cytoplasm
- Ghost cells present
- Mechanism is protein degradation
- Examples-
- Ischemia
- Thermal Injury
- Dry gangrene
- Zenkers degeneration: Necrosis of rectus abdominis muscle in typhoid fever
Liquefactive Necrosis
- Caused by digestion of dead cells resulting in a viscous liquid
- Plasma membrane is completely dissolved, hence cell outline is not seen.
- Neutrophilic infiltration visible
- Associated with bacterial/fungal infections
- Mechanism is Lipase activation
- Examples-
- Brain, Pancreas
- Abscess- Wet Gangrene
- Ischemia to brain and spinal cord
- Coagulative necrosis accompanied by bacterial infection
Caseous Necrosis
- Usually in India associated with TB infection
- On gross, necrotic areas appear cheesy white, caseous, granular
- Examples-
- Miliary Tuberculosis of any organ
- Syphilis
- Histoplasmosis
- Coccidiomycosis
Fat Necrosis
- Local area of fat destruction
- Fat cell necrosis accompanied by liquefactive necrosis
- Mechanism can be enzymatic or traumatic
- Enzymatic mechanism-(Add downward pointing vertical arrow after each point to make it a flow chart)
- Acute pancreatitis
- Enzyme activation
- Liquefaction of pancreas
- Fat diffuses out
- Peripancreatic Fat omentum
- Fat necrosis
- Traumatic mechanism-
- Occurs in any fat rich region
- Breast-
- Macrocalcification – traumatic fat necrosis
- Microcalcification – DCIS Comedo Necrosis
- Examples-
- Acute pancreatitis
- Traumatic fat necrosis of breast
Fibrinoid Necrosis
- A form of vascular damage
- Fibrin like morphology appears homogenous pink color
- Examples-
- Vasculitis- Inflammation of blood vessels
- Malignant hypertension
- Immune complex (Antigen-antibody complexes) deposited in walls of arteries
- Type III Hypersensitivity
- Rheumatic Heart Disease