INFLAMMATION: Cellular Patterns

Focal inflammation
Focal invasion of muscle fiber
Muscle fiber necrosis

Also see:
  Inflammatory myopathy

Focal lymphocytic inflammation: Nongranulomatous

Nodular inflammation

  • Accumulation of lymphocytes with small dark nuclei (Left)
  • Only a minority of cells are esterase positive (Right)


Differential diagnosis
  Giant cells
  Other: Tissue changes

Congo red stain
Cells in granuloma
  Central: Histiocytes
  Periphery: Lymphocytes

Esterase stain
Cells in granuloma
  Confluent esterase

CD68 stain
Cells stain for
  Acid phosphatase
  CD68 antigen

Granulomas: Differential Diagnosis
H&E stain

Granulomas: Features
  Focal cell collections
    Histiocytic cells
      Location: Central
      Nuclei: Large
      Cytoplasm: Prominent
      Stain with
        Acid phosphatase: Perinuclear
        Esterase: Cytoplasm
        Antibodies: CD68; CD4
    Giant cells: Markers
      Absent: Myoglobin
      Location: Peripheral
      Nuclei: Small; Dark
      Cytoplasm: Little
      Component: γδ T-cells
  Humoral Factors: associated

H&E stain

H&E stain

Histiocytic cell location: May occupy region of lost muscle fiber

Congo red stain

Granulomas: Locations & Staining Patterns

Granuloma location: May cross tissue borders

Congo red stain
Granuloma extending into both Endomysium & Perimysium
Also see: Granuloma extending into both Endoneurium & Perineurium

Granuloma location: Perimysial Granuloma

Congo red stain
Granuloma contains
  Large histiocytic cells: Have abundant cytoplasm & large nuclei
  Giant cell

Gomori trichrome stain

Acid phosphatase stain
Acid phosphatase (Above): Stains perinuclear region of granuloma cells
  This differs from the confluent staining in IMAM cell foci

Esterase (Below) shows confluent staining of cells in granulomas

Esterase stain

Granulomatous Disease: Perimysium

H&E stain

Granuloma in perimysium

Congo red

Acid phosphatase stain

Granulomatous Myopathy, Chronic

  Muscle fibers
    Varied size: Hypertrophy & Atrophy
    Internal nuclei

H&E stain

Granuloma location: Endomysial Granuloma

H & E stain
Large cells in granuloma

Esterase stain
Confluent staining of cells in granuloma

Acid phosphatase stain
Perinuclear staining of most cells in granuloma

Granulomatous myopathy: Muscle fiber pathology
Focal invasion & replacement of non-necrotic muscle fiber by granuloma cells
  Granuloma cells: Large & Stain with acid phosphatase
  Muscle fibers: Progressively invaded & replaced by granuloma cells (Arrows)
Acid phosphatase stain

Erosion of non-necrotic muscle fibers around & along their edges


MHC expression by muscle fibers & granuloma cells

Control muscle: MHC expression only in vessels

Other immune features
Alkaline phosphatase staining of perimysium

CD4 staining of granuloma cells

Giant cells, Multinucleated

Frozen sections

Congo red
Giant cells, Multinucleated
  Size: Very large
  Nuclei: Several in one cell; Large
  Cytoplasm: May stain strongly for lysosomal markers

H&E stain

H&E stain

Congo red stain

Giant cells stain for acid phosphatase (Arrow)

Acid phosphatase stain

Fixed muscle sections

H&E stain

H&E stain

H&E stain

Granulomatous Myopathy: Connective tissue pathology, Epimysial & Perimysial

Acid phosphatase stain

H&E stain
Non-Granulomatous Histiocytic Cellularity: Scattered cells

Acid phosphatase stain

MHC Class I stain

Granulomatous Disease:
  Nerve, Perivascular

VvG stain
Axon loss: Myelinated axons
  Variable within fascicles

Acid phosphatase stain
Histiocytic perivascular cells

Toluidine blue stain
Axon loss
  Large & Small myelinated
Regenerating clusters: Small, Few

Toluidine blue stain
Cells in Vessel Walls
  Size: Large
  Nuclei: Large
  Cytoplasm: Abundant

Granulomatous Disease:
  Nerve, Endoneurial & Perineurial

Granulomas: Endoneurial & Perineurial
  Clusters of large cells extending into perineurium & endoneurium
Granulomas: Endoneurial & Perineurial
  Clusters of large cells
    Cells have large nuclei & abundant cytoplasm
    Some cells contain lipid droplets

Granulomatous Changes: Tuberculosis (Cerebellum)

Regional changes
Necrotic tissue (Top Right)
Granulomatous pathology (Bottom Left)
  Multinucleated giant cells
  Histiocytic cells: Scattered

H&E stain

Granulomatous tissue
  Multinucleated giant cells
  Scattered histiocytes

H&E stain

Tuberculous bacilli
  Small, red-stained structures

Acid fast stain

Return to Inflammatory myopathies
Return to Neuromuscular Syndromes
Return to Neuromuscular Home Page