Macrophagic Myofasciitis (MMF)

Also see: Inflammatory Myopathy with Abundant Macrophages (IMAM)

H&E stain

H&E stain

H&E stain
  • Cell foci & Infiltrates
    • Location: Endomysium > Perimysium.
    • Cells
      • Large
      • Abundant cytoplasm
      • Histiocytic: Esterase & Acid phosphatase positive
      • Lipid: Moderate levels
      • Contain: Aluminum (Morin stain)
    • Not granulomas
  • Muscle fibers
    • Not prominently affected.
    • No degeneration or regeneration.
  • Fascia (Perimysium): No necrosis

H&E stain
Nuclei: Large; Irregular shapes

Congo red stain

Cells in infiltrates   Mostly histiocytic
  Stain strongly with: Esterase & Acid phosphatase.

Esterase stain

Esterase stain

Esterase stain

Acid phosphatase stain
MMF cells:
  Confluent, strong acid phosphatase staining;
  Individual cell outlines in foci not visible

Acid phosphatase stain

VvG stain
MMF cells contain cytoplasmic lipid: Stains with VvG and Sudan

Sudan stain

PAS stain
Cells also stain moderately with PAS

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