Definition: a type of necrosis characterized by small blood vessel injury with accumulation of fibrin and other plasma proteins.
Pathophysiology: vessel wall damage caused by immune complex deposition (e.g., due to type III hypersensitivity reaction) → fragmentation of collagenous and elastic fibers → leakage of fibrin and other plasma proteins
Microscopic appearance
Visible damage: thick walls with fragments of embedded cellular debris, serum, and fibrin