Fibrosarcoma of the bone is a rare malignant bone tumor which may occur as a primary lesion, or secondarily after radiation treatment, dedifferentiation from other tumors 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 tumors. 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 mineralization, but may have areas of sequestered bone. These tumors 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
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The differential diagnosis for bone tumors is dependent on the age of the patient, with a very different set of differentials for the pediatric patient.
- bone-forming tumors
- cartilage-forming tumors
- chondromyxoid fibroma
- juxtacortical chondroma
- fibrous bone lesions
- bone marrow tumors
- other bone tumors or tumor-like lesions
- aneurysmal bone cyst
- benign fibrous histiocytoma
- giant cell tumor of bone
- Gorham massive osteolysis
- haemophilic pseudotumor
- intradiploic epidermoid cyst
- intraosseous lipoma
- musculoskeletal angiosarcoma
- musculoskeletal hemangiopericytoma
- primary intraosseous hemangioma
- post-traumatic cystic bone lesion
- simple bone cyst
- impending fracture risk