A fibrosarcoma that occurs in infants. It shares identical morphologic features with adult fibrosarcoma but carries the t(12;15)(p13;q25) translocation that results in ETV6-NTRK3 gene fusion. It usually affects the superficial and deep soft tissues of the extremities. The prognosis is generally much more favorable than for adult fibrosarcoma, and it rarely metastasizes. The disease is Monarch Disease Ontology id MONDO_0004557 (congenital fibrosarcoma). Also known as: infantile fibrosarcoma, infantile fibrosarcoma (congenital fibrosarcoma), infantile fibrosarcoma (morphologic abnormality).