Fibrosarcoma

Fibrosarcoma is a rare malignant tumor that arises from fibroblasts, the cells responsible for producing connective tissue (fibrous tissue) throughout the body. It belongs to the group of soft tissue sarcomas and is characterized by the proliferation of immature fibroblasts or undifferentiated anaplastic spindle cells. Fibrosarcoma can occur in soft tissues such as muscles, tendons, fascia, and fat, most commonly affecting the extremities (particularly the thigh and knee region), but it can also arise in the trunk, head, and neck. The tumor typically presents as a slow-growing or rapidly enlarging painless mass, though pain may develop as the tumor compresses surrounding structures. Metastasis, particularly to the lungs, can occur. There are two main clinical forms: adult-type fibrosarcoma, which typically occurs in individuals between 25 and 79 years of age, and infantile (congenital) fibrosarcoma, which presents at birth or during the first two years of life. Infantile fibrosarcoma is associated with a characteristic chromosomal translocation t(12;15)(p13;q25) resulting in the ETV6-NTRK3 fusion gene, and generally carries a more favorable prognosis than the adult form. Adult fibrosarcoma is graded based on cellularity, differentiation, mitotic activity, and necrosis, with higher-grade tumors having a worse prognosis. Treatment of fibrosarcoma primarily involves wide surgical excision with adequate margins to minimize local recurrence. Radiation therapy may be used as an adjunct, particularly when complete surgical resection is not achievable or when margins are close or positive. Chemotherapy may be considered for high-grade tumors, metastatic disease, or unresectable cases. For infantile fibrosarcoma harboring NTRK fusions, targeted therapies such as larotrectinib and entrectinib (TRK inhibitors) have shown remarkable efficacy and represent a significant advance in treatment. Overall prognosis depends on tumor grade, size, location, and the adequacy of surgical resection.

Data sourced from FDA regulatory filings and ClinicalTrials.gov. Updated periodically.

Common questions about Fibrosarcoma