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Clinical features

  • Young adults
  • Male predominance
  • Superficial or deep lesions
  • No predilection for anatomic site
  • Solitary lesions
  • When deep and multiple- association to neurofibromatosis Type I or II
  • Malignant transformation- more frequent in patients with neurofibromatosis Type I


  • Painful aspiration
  • Poor cellularity
  • Cystic /myxoid background
  • Single cells or small aggregates
  • Slim and elongated spindle to stellate nuclei
  • Nuclei with tapered ends
  • Bland chromatin
  • Nuclear Pleomorphism and  hiperchromasia can be present
  • Mitosis are exceptional
  • Schwann cell and fibroblastic cells


  • Schwann cells
    • S100 protein: Positive
  • Fibroblasts
    • CD34: Positive
  • Axons: highlighted with neurofilaments
  • EMA: positive (Plexiform subtype)

Differential Diagnosis

  • Schwannomas
    • Nuclear features are in most of the cases indistinguishable
    • Cell block can be helpful-Palisade
    • The essential diagnosis is that of a benign Neutrogena tumour
  • *Liposarcoma myxoid
    • Atypical Lipoblasts

Main points

  • Malignant transformation rare in sporadic presentations (5% of Plexiform forms transform in Malignant peripheral nerve sheath tumour)