Definition: Benign tumor consisting of a mixture of cell types including Schwann cells, perineurial-like cells and fibroblasts.

Growth pattern

 localized
 diffuse
 plexiform

Localized neurofibroma

• 90% sporadic, 10% in the setting of neurofibromatosis 1 (NF1)
• most develop between 20-30 years
• in a major nerve :
  • fusiform expansion
  • confined by the epineurium
• in a small nerve :
  • extension in soft tissues
  • circumscribed but not encapsulated

• histology :
  • interlacing bundles of cells with ovoid-to-spindle, often curved, nuclei
  • collagen fibres and myxoid matrix

Plexiform neurofibroma

• pathognomonic of neurofibromatosis 1 (NF1)
• develop during early childhood
• affects large segments of a nerve (aspect of a bag of worms)

• histology :
  • tortuous enlargement of nerve branches
  • expansion of the endoneurium by myxoid matrix
  • possible nuclear atypia
  • malignant transformation : MPNST

Diffuse neurofibroma

• children and young adults
• 10% arise in the setting of neurofibromatosis 1 (NF1)
• ill-defined infiltration of subcutaneous tissue
  • matrix of fine fibrillary collagen
  • rather fusiform of rounded Schwann cells
  • clusters of Meissner body-like structures

Cytogenetics

 unbalanced t(2;19) (#15262441#)
 unbalanced t(2;16) (#15262441#)