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WHO Classification of Tumours
Fibrosarcoma, NOS


Fibrosarcoma is a malignant mesenchymal tumour affecting soft tissues and bone. It is classified as adult or infantile. Infantile fibrosarcomas generally have a more favourable prognosis than those manifesting in adults.
Primary fibrosarcoma of bone most frequently involves the metaphyses of long bones. The tumours are composed of spindle shaped cells arranged in a fascicular or "herringbone" pattern. Histollogically, fibrosarcomas range from well differentiated tumours, which are difficult to separate from desmoplastic fibroma , to highly malignant tumours which are composed of small cells and resemble Ewing sarcoma . Well differentiated lesions produce large amounts of collagen, resulting in a firm consistency with a trabeculated cut surface and circumscribed margins. Poorly differentiated tumours have a softer, fleshy consistency, with foci of necrosis. Cortical destruction and soft tissue extension are common.
Fibrosarcomas of bone occur relatively uniformly over the second to sixth decades. The most important prognostic factor is histological tumour grade

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Fletcher CDM, Unni KK, Mertens F (Eds.)
World Health Organization Classification of Tumours. Pathology and Genetics of Tumours of Soft Tissue and Bone.
3rd Edition
IARC Press: Lyon 2002