Fibrosarcoma of the bone is a rare malignant bone tumour which may occur as a primary lesion, or secondarily after radiation treatment, dedifferentiation from other tumours 3 or pathologies such as Paget disease, bone infarction, or chronic osteomyelitis.
It is a distinct entity from but similar to malignant fibrous histiocytoma 2 (pleomorphic undifferentiated sarcoma) that may also rarely occur in bone, causing confusion in terminology, as the term "fibrosarcoma" has in the past encompassed a multitude of distinct histologic diseases.
Fibrosarcoma occurs primarily in 30-60-year-olds, with a slight male predominance. It constitutes <5% of primary bone tumours. Infantile fibrosarcoma is also rarely encountered in bone.
Cells are fibroblastic in appearance with a somewhat uniform spindle shape. They may be arranged in fascicles creating a herringbone pattern. The degree of differentiation is variable, however, and therefore distinguishing features from other spindle cell neoplasm should be sought. Extracellular collagen fibrils are typical.
Typically highly destructive with a wide zone of transition, and occasionally expansile. Periosteal reaction is uncommon, but if seen is usually laminated, spiculated or Codman triangles. The lesion usually has no matrix mineralisation, but may have areas of sequestered bone. These tumours are often associated with a large soft tissue mass extending from the bone 1.
MRI is useful in defining intraosseous spread and the extent of extension into the soft tissues. Descriptions of the appearance of intraosseous fibrosarcoma on MR are few.
The signal intensity pattern is nonspecific:
- T1: isointense to muscle
- T2: hyperintense to muscle
- T1C+: avid contrast enhancement (may be uniform or heterogeneous)
- 1. Resnick DL. Diagnosis of bone and joint disorders. Saunders. (2002) ISBN:0721689213. Read it at Google Books - Find it at Amazon
- 2. Antonescu CR, Erlandson RA, Huvos AG. Primary fibrosarcoma and malignant fibrous histiocytoma of bone-a comparative ultrastructural study: evidence of a spectrum of fibroblastic differentiation. Ultrastruct Pathol. 2000;24 (2): 83-91. Pubmed citation
- 3. Qu N, Yao W, Cui X et-al. Malignant transformation in monostotic fibrous dysplasia: clinical features, imaging features, outcomes in 10 patients, and review. Medicine (Baltimore). 2015;94 (3): e369. doi:10.1097/MD.0000000000000369 - Pubmed citation
The differential diagnosis for bone tumours is dependent on the age of the patient, with a very different set of differentials for the paediatric patient.
- bone-forming tumours
- cartilage-forming tumours
- chondromyxoid fibroma
- fibrous bone lesions
- bone marrow tumours
- other bone tumours or tumour-like lesions
- aneurysmal bone cyst
- benign fibrous histiocytoma
- giant cell tumour of bone
- Gorham massive osteolysis
- haemophilic pseudotumour
- intradiploic epidermoid cyst
- intraosseous lipoma
- musculoskeletal angiosarcoma
- musculoskeletal haemangiopericytoma
- primary intraosseous haemangioma
- simple bone cyst
- impending fracture risk