Updated: 12/2/2017

Neurilemmoma

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 Introduction
  • A benign encapsulated tumor composed of Schwann cells
    • tumor is well encapsulated on the surface of a peripheral nerve
    • also known as Schwannoma
  • Age & location
    • peak incidence is in the 3rd to 6th decades
      • previous test question ages: 40, 45
    • affect males and females equally
    • often occurs on flexor surfaces of extremities and head and neck
    • larger lesions may occur in the pelvis
  • Pathoanatomy
    • can affect motor or sensory nerves
  • Genetics
    • often associated with mutations affecting NF2 gene
  • Malignant transformation
    • extremely rare
 Presentation
  • Symptoms
    • usually asymptomatic
    • may have paresthesia in the distribution of the peripheral nerve
  • Physical exam
    • may have positive Tinel’s sign in the distribution of the nerve affected may be present
 Imaging
  • MRI
    • sequences
      • low intensity (dark) T1
      • high intensity (bright) on T2
      • diffuse enhancement with gadolinium
    • findings
      • may show “string sign”  
      • difficult to differentiate from neurofibroma
 Histology
  • Gross pathology
    • the lesion is well encapsulated in a nerve sheath 
    • gray in color
  • Histology   
    • Antoni A structure 
      • a pattern of spindle cells arranged in intersecting bundles (spindle cell battle formation
    • Antoni B
      • areas with less cellularity with loosely arranged cells
    • Verocay bodies   
      • pathognomonic 
      • composed of two rows of aligned nuclei in a palisading formation
  • Immunochemistry
    • strongly uniform S100 antibody staining
 Treatment
  • Nonoperative
    • observation
      • indications
        • asymptomatic lesions
  • Operative
    • marginal excision 
      • indications
        • symptoms or interfering with quality of life
      • technique
        • nerve function may be preserved by careful dissection, excising the lesion parallel to the nerve fascicles so the lesion may be extruded. 
      • complications
        • small risk of sensory deficits
      • outcomes
        • recurrence is rare
 

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