Bone and Soft-Tissue Disorders
Frequency: 4% of all primary bone neoplasm
Etiology:
- PRIMARY FIBROSARCOMA (70%)
- SECONDARY FIBROSARCOMA (30%)
- following radiotherapy of giant cell tumor / lymphoma / breast cancer
- underlying benign lesion: Paget disease (common); giant cell tumor, bone infarct, osteomyelitis, desmoplastic fibroma, enchondroma, fibrous dysplasia (rare)
- dedifferentiation of low-grade chondrosarcoma
Histo: spectrum of well to poorly differentiated fibrous tissue proliferation; will not produce osteoid / chondroid / osseous matrix
Age: predominantly in 3rd5th decade (range, 888 years); M÷F = 1÷1
Metastases to: lung, lymph nodes
Location: tubular bones in young, flat bones in older patients; femur (40%), tibia (16%) (about knee in 3050%), jaw, pelvis (9%); rare in small bones of hand + feet or spinal column
Site: eccentric at diaphyseal-metaphyseal junction into metaphysis; intramedullary / periosteal
- CENTRAL FIBROSARCOMA
= intramedullary
- well-defined lucent bone lesion
- thin expanded cortex
- aggressive osteolysis with geographic / ragged / permeative bone destruction + wide zone of transition
- occasionally large osteolytic lesion with cortical destruction, periosteal reaction + soft-tissue invasion
- sequestration of bone may be present (DDx: eosinophilic granuloma, bacterial granuloma)
- sparse periosteal proliferation (uncommon)
- intramedullary discontinuous spread
- no calcification
DDx: malignant fibrous histiocytoma, myeloma, telangiectatic osteosarcoma, lymphoma, desmoplastic fibroma, osteolytic metastasis - PERIOSTEAL FIBROSARCOMA
= rare tumor arising from periosteal connective tissue
Location: long bones of lower extremity, jaw
- contour irregularity of cortical border
- periosteal reaction with perpendicular bone formation may be present
- rarely extension into medullary cavity
Cx: pathologic fracture (uncommon)
Prognosis: 20% 10-year survival
DDx:
- Osteolytic osteosarcoma (2nd3rd decade)
- Chondrosarcoma (usually contains characteristic calcifications)
- Aneurysmal bone cyst (eccentric blown-out appearance with rapid progression)
- Malignant giant cell tumor (begins in metaphysis extending toward joint)