Introduction
Fibrosarcoma is a tumor of mesenchymal cell origin that is composed of malignant fibroblasts in a collagen background. It can occur as a soft-tissue mass or as a primary or secondary bone tumor. Fibrosarcoma was diagnosed much more frequently in the past; it is now more reliably distinguished histologically from similar lesions, such as desmoid tumors, malignant fibrous histiocytoma, malignant schwannoma, and high-grade osteosarcoma.
The 2 main types of fibrosarcoma of bone are primary and secondary. Primary fibrosarcoma is a fibroblastic malignancy that produces variable amounts of collagen. It is either central (arising within the medullary canal) or peripheral (arising from the periosteum). Secondary fibrosarcoma of bone arises from a preexisting lesion or after radiotherapy to an area of bone or soft tissue. This is a more aggressive tumor and has a poorer prognosis.
History of the Procedure
As with all soft-tissue and bone sarcomas, the mainstay of treatment for fibrosarcoma has been complete excision with an adequate margin; this procedure became prevalent following the publication and wide acceptance of Enneking's surgical principles of musculoskeletal oncology, in the early 1980s. This surgery normally consists of resecting a cuff of normal tissue along with the tumor.
Problem
As with all sarcomas, the long-term survival and ultimate functional outcome of cancer treatment depend on many interrelated factors. Among these are the size and location of the tumor, its histologic grade, and the presence of metastatic disease (eg, pulmonary metastases). These factors are taken into account with careful evaluation (staging) of the tumor and determine the success of treatment in obtaining good local control and preventing subsequent disease spread.
Frequency
Fibrosarcoma represents only about 10% of musculoskeletal sarcomas and less than 5% of all primary tumors of bone. No known racial predilection exists.
Fibrosarcoma of bone occurs slightly more commonly in men than in women.
Fibrosarcoma of bone can be diagnosed in patients of any age, but it is diagnosed more commonly in patients in the fourth decade of life. It is usually located in the lower extremities, especially the femur and tibia.
Fibrosarcoma of the soft tissues usually affects a wider age spectrum of patients than fibrosarcoma of the bone does, with an age range of 35-55 years. It often arises in the soft tissues of the thigh and the posterior knee. It is generally a large, painless mass deep to fascia and has an ill-defined margin.
An infantile form (in children <10 y) of fibrosarcoma exists. Unlike fibrosarcoma in adults, it has an excellent prognosis—even in the face of metastatic disease at presentation—when treated with a combination of neoadjuvant and adjuvant chemotherapy and resection.
Etiology
Fibrosarcoma, like other soft-tissue sarcomas, has no definite cause. Current research indicates that many sarcomas are associated with genetic mutations. The more common genetic defects include allele loss, point mutations, and chromosome translocations. See Pathophysiology for a discussion of associated conditions.
Pathophysiology
No definite cause of fibrosarcoma is known, although genetic mutations may play a role. Several inherited syndromes are associated with sarcomas. For example, patients with multiple neurofibromas may have a 10% lifetime risk of developing a neurosarcoma or a fibrosarcoma.
The occurrence of fibrosarcoma in conjunction with metallic implants used for fracture fixation or joint reconstruction has been reported, albeit very rarely. The cause of this transformation is unknown.
Fibrosarcoma has also been noted to arise from preexisting lesions, such as bone infarcts and lesions associated with fibrous dysplasia, chronic osteomyelitis, and Paget disease, as well as in previously irradiated areas of bone. This form of fibrosarcoma is very aggressive and is associated with a much poorer outcome than is the primary fibrosarcoma of bone.
Presentation
Sarcomas involving bone often present with pain and swelling after a long duration of symptoms. They may even grow large enough to threaten the structural integrity of the bone and cause pathologic fracture as the initial presentation. Generally, lesions that involve more than 50% of the bone cortex, that are larger than 2 cm, or that involve the medial calcar of the femur are associated with the greatest risk of fracture. A prior history of bone infarct, irradiation, or other such risk factors should alert the physician to the possibility of a secondary fibrosarcoma.
Soft-tissue sarcomas most often present as painless masses. The time to presentation, however, is often shorter than with lesions involving bone. Because these lesions frequently arise deep to the muscular fascia, they may become extremely large tumors prior to diagnosis.
Most lesions occur around the knee, in the proximal femur and hip region, or in the proximal arm. Findings are nonspecific and can vary from a fixed, firm mass to a localized area of tenderness. Neurologic or vascular changes are late findings and indicate extensive disease involvement.
Differential diagnoses include the following:
- Fibrous dysplasia
- Fibrous histiocytoma
- Osteosarcoma
- Paget sarcoma
- Malignant fibrous histiocytoma
- Malignant neurosarcoma
Indications
To obtain local control, surgical resection with a cuff of normal tissue (wide margins) and reconstruction of the subsequent defect are necessary.
Relevant Anatomy
See Introduction, Clinical.
Contraindications
Surgical treatment (including biopsy) of fibrosarcoma should not proceed unless complete patient care is available. Complete care includes biopsy and interpretation of biopsy findings, access to oncologists and radiation oncologists, and definitive resection.
Fibrosarcomas should be removed by trained orthopedic oncologists who can provide a state-of-the-art treatment program; this would involve a team of well-trained specialists with advanced experience in treating these tumors.
More on Fibrosarcoma |
 Overview: Fibrosarcoma |
| Workup: Fibrosarcoma |
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Further Reading
Keywords
mesenchymal cell tumor, malignant fibroblasts, fibroblastic malignancy
