Neurofibroma

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

Cytopathology

• 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

Immunocytochemistry

• 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)