Nodular fasceiitis

Clinical features

  • Frequent in the first two decades of life
  • History of rapid growing (weeks)
  • Most common locations: upper extremities, head, neck, chest or back
  • Small size lesions-2-3 cm
  • Subcutaneous, in children and young adults
  • Rarely in neonates
  • Previous trauma in 10% to 15%

 

Fig 29 - Nodular fasciitis- Myxoid spindle cell lesion
Fig 30 - Nodular fasciitis- bland looking but pleomorphic myofibroblasts and inflammatory cells (H&E)

 

 

  • Hypercellular smear
  • Recognition of a myxoid spindle cell lesion in 5% of the cases
  • Dispersed to cohesive cells
  • Bland looking, but pleomorphic myofibroblasts (plump, spindle, ovoid, kidney-shaped nuclei)
  • Binucleated forms
  • Triangular cells
  • Eccentrically placed nuclei with bland chromatin
  • Ganglion cell-like
  • Frequent mitosis
  • Inflammatory cells (neutrophils, lymphocytes, eosinophils) histiocytes and/or multinucleated giant cells)

 

Immunocytochemistry

  • Vimentin: Positive
  • CD68: Positive
  • Smooth muscle actin: Positive
  • Calponin: Positive
  • Desmin: Negative
  • S100 protein: Negative
  • CD34: Negative

 

Genetic studies

  • MYH9-USP6 fusion gene

 

Differential Diagnosis

  • Myxoid liposarcoma
    • Lipoblasts
    • Absence of inflammatory background
  • Malignant fibrous histiocytoma
    • More atypia
  • Schwannoma
    • Marked cellularity
    • Less single cells
    • Rare/no mitosis
    • No inflammatory background
    • Prominent stromal fragments with hypercellular and hypocellular areas
    • Verocay bodies
    • Palisade
    • S100 protein: Positive

 

Main points

  • Self-healing in 3-4 weeks
  • Local excision can be an adequate treatment
  • In conjunction with clinical presentation, cytology can be diagnostic
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