PARANEOPLASTIC NECROTIZING MYOPATHY

Paraneoplastic Necrotizing Myopathy Acute stage   Regions of necrotic muscle fibers   H&E stain H&E stain Numerous muscle fibers in stages of necrosis. Some necrotic muscle fibers are being phagocytosed by macrophages.

Paraneoplastic Necrotizing Myopathy Subacute stage   Regenerating & Necrotic muscle fibers H&E stain NADH stain Numerous small, basophilic muscle fibers with large nuclei. Coarse internal architecture on NADH stain.

Paraneoplastic Necrotizing Myopathy Immune changes: No mononuclear cells
Esterase stain Esterase stain Large, esterase positive macrophages in endomysium. Phagocytosis of a muscle fiber.	Alkaline phosphatase stain Alkaline phosphatase stains perimysium,   endomysium and some regenerating muscle fibers.

Paraneoplastic Necrotizing Myopathy: Complement Deposition (C5b-9)

	Terminal components of complement (C5b-9; Membrane attack complex) deposited in large clusters of muscle fibers

Paraneoplastic Necrotizing Myopathy: MRI

T2: No contrast
Increased T2 signal in patchy regions of muscle & connective tissue