Neuromuscular

Immune Checkpoint Inhibitors

Immune Neuropathies
  Endoneurial Microvessel Inflammation
  Perineuritis/Epineuritis

Polyradiculoneuropathy + Endoneurial Inflammatory Vasculopathy (Ipilimumab)


MRI: Root enhancement
MRI: Meningeal enhancement

Endoneurial Microvessels: Perivascular inflammation


H&E stain

CD163 stain
Inflammation: Endoneurial; Perivascular

H&E stain

CD3 stain

CD163 stain

Acid phosphatase stain


Toluidine blue stain

Toluidine blue stain
Subperineurial Edema

VvG stain

Perineuritis/Epineuritis/Vasculopathy: ICI-related


H&E stain
Perineurium
  Pale & Wide around most fascicles
Epineurium
  Structure: Irregular & Pale


MHC Class I stain
MHC Class I
  Abnormally & Diffusely expressed in Epineurial connective tissue


H&E stain
Perineurium
  Pale & Wide around most fascicles
Epineurium
  Structure: Irregular & Pale
Endoneurium
  Wallerian Degeneration: Myelin irregularly stained, may be pale

VvG stain

Loss of large axons

Neurofilament stain

Perineurial Pathology


H&E stain
Perineurium
  Pale & Wide
  Some areas have increased cells

H&E stain

Perineurium
  Pale & Wide
Endoneurium
  Wallerian Degeneration: Myelin irregularly stained & may be pale

VvG stain

ICI Perineuriopathy: C5b-9 stain
  Perineurium: Loss of C5b-9 stain
  Endoneurium: C5b-9 stains cells associated with Wallerian degeneration
  Epineurium: C5b-9 stains scattered cells

C5b-9 stain

Control Nerve
  Perineurium: Strong C5b-9 stain

C5b-9 stain


Toluidine blue stain
Perineurium
  Pale & Wide
Endoneurium
  Loss of most myelinated axons: Varied between fascicles

Toluidine blue stain

Epineurium
  Structure: Irregular & Pale

H&E stain


CD4 stain
Epineurial Cells
  Scattered
  Stain for CD4 & CD8
Perineurial Cells
  Mostly CD8

CD8 stain

Epineurial & Endoneurial Cells
  Many Histiocytes

HAM56 stain

ICI Myopathy


Perimysial Connective Tissue
  Widened
  Cellular
Muscle fibers
  Perifscicular pathology
  Scattered, small fibers at edge of some fascicles, near perimysial damage

H&E stain

H&E stain

Acid phosphase stain

Esterase stain

Alkaline Phosphatase stain

MHC I stain

C5b-9 stain

ICI Myopathy: Case 2


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4/8/2024