MUSCLE FIBER NECROSIS

General features

• Associated with break in, or absence of, muscle surface fiber membrane
• Results in irreversible damage to region of muscle fiber
• Staining
  • H & E: Pale in necrotic region; Dark in neighboring hypercontracted region
  • Positive for complement MAC within muscle fiber

Morphology

H & E Stain	Normal muscle fiber
	Necrotic muscle fiber: Pale
	Necrotic muscle fiber:   Phagocytosis by macrophages
	Hypercontracted necrotic muscle fiber
	Perimysium

H&E	Esterase stain
Necrotic muscle fiber, Early (left) Fiber is pale & enlarged. Internal nuclei may reflect invasion by macrophages.	Necrotic muscle fiber, Late Fiber is invaded by macrophages.

Toluidine blue stain Longitudinal section: Pale necrotic muscle fiber invaded by cells
Toluidine blue stain Cross-section: Pale necrotic muscle fiber invaded by cells	Toluidine blue stain Necrotic muscle fiber

Toluidine blue stain Cells in necrotic fiber

Toluidine blue stain Non-necrotic muscle fiber: Dilated SR (Left)

Necrotic muscle fibers: Complement C5b-9 (MAC) deposition

Stain: C5b-9 components of complement (Membrane attack complex (MAC)) Necrosis: C5b-9 deposition diffusely within muscle fibers