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Non-Rhabdomyosarcoma (Non-RMS)



Infantile Fibrosarcoma (IF)



Infantile fibrosarcoma (IF) is also referred to as Congenital Infantile fibrosarcoma (CIFS) and Congenital fibrosarcoma (CFS).

This is very rare and occurs primarily in the first year of life and accounts for 5 - 10% of all sarcomas in infants less than one year of age. This tumor offen occurs in newborns and is most common in children less than 2 years of age.

Associated with a specific chromosomal translocaton:

  • Reciprocal translocation t(12;15)(p13;q25)
  • Resulting in the gene fusion ETV6-NTRK3 (ETS variant gene 6; neurotrophic tyrosine kinase receptor type 3)
  • These chromosomal changes are also present in the cellular form of congenital mesonephroblastic nephroma

The prognosis is good and is 80 - 90% overall survival at 5 years and these tumors rarely metastasize. The risk of metastatic disease is about 10%.

Presenting complaint: Rapidly enlarging mass involving the trunk or extremities



  • Histological appearance is very similar to adult type high grade fibrosarcoma
  • Malignant (high cellularity, nuclear atypia, increased mitotic activity and necrosis)
  • To differentiate this tumor from other pathological subtypes of non-RMS a reverse transcription-polymerase chain reaction (RT-PCR) assays have been developed to detect ETV6-NTRK3 fusion transcripts in IF frozen or paraffin-embedded tumor specimens.




Molecular Detection of the ETV6-NTRK3 Gene Fusion Differentiates Congenital Fibrosarcoma From Other Childhood Spindle Cell Tumors.  Bourgeois, Jacqueline M. M.D.; Knezevich, Stevan R. Ph.D.; Mathers, Joan A. A.R.T.; Sorensen, Poul H. B. M.D., Ph.D.







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