Fibrosarcoma of infancy

Clinical features

  • Usually presents before the age of 2
  • 50% congenital
  • Axial regions and extremities
  • Male predominance
  • Rapid growth
  • Extensive local invasion

 

Cytopathology

  • Cellularity and degree of pleomorphism depends on the histological grade
  • Cells with ovoid to elongated nucleus
  • Fine granular chromatin
  • Small nucleoli
  • Scant to moderate uni or bipolar cytoplasm
  • Nuclear atypia
  • Necrosis
  • Mitosis are frequent , although not important to prognosis
  • Immunocytochemistry
  • Vimentin: Positive
  • Smooth muscle actin: Positive( focal)
  • Desmin: Positive ( focal)
  • S100 Protein: Positive( focal)
  • CD34: Positive( focal)
  • Factor XIIIa: Positive

 

Genetic studies

  • t(12;15)(p13;q25)- ETV6-NTRK3 gene fusion (in 70%)
  • Trisomy of chromosome 11
  • Variable trisomy’s of chromosomes 17 and 20 or 8 and 10

 

Differential Diagnosis

  • Nodular fasciitis
    • Typical clinical presentation
    • Highly characteristic metachromatic myxoid stroma
    • Cells loosely and haphazardly arranged in fragments
  • Fibromatosis
    • Less cellularity than fibrosarcoma
    • Bland spindle nuclei
    • Inconspicuous nucleoli
    • Absence of mitosis
  • Embryonal Rhabdomyosarcoma
    • Myxoid stroma
    • Desmin: Positive
    • Myo-D1: Positive
  • Synovial Sarcoma
    • Cytokeratins: Positive
    • t(X; 18) (p11.2; q11)

 

Main points

  • Identical  to congenital mesoblastic nephroma
  • 90% survival
  • 40-50% recur
  • 10% metastasize (typically to the lung)

Treatment: complete excision

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