- Author: Ian D Dickey, MD, FRCSC; Chief Editor: Harris Gellman, MD more...
Plain radiographs of the involved anatomic region are needed to evaluate for primary or secondary involvement of bone. (See the image below.) Typically, an osteolytic area of destruction with a permeative or moth-eaten appearance is present. Little periosteal reaction or reactive sclerosis is depicted.
For bony lesions, plain radiographs often greatly assist in diagnosis and the determination of location, size, and local extent of involvement. For soft-tissue masses, size often can be estimated, any bone involvement can be seen, and intralesional content (matrix) can sometimes be determined.
For sarcomas arising in bone, computed tomography (CT) is used to delineate bone involvement, bone destruction, or bone reaction. The density of fibrosarcomas is similar to that of surrounding normal muscle. Signs of fracture or impending fracture may be seen, and the tumor can be more accurately localized. CT of the chest may be appropriate. CT is highly sensitive for metastatic disease.
Magnetic resonance imaging
Magnetic resonance imaging (MRI) may be the best modality overall for examining soft-tissue masses and for detecting the intraosseous and extraosseous extent of many bony sarcomas. It is useful in providing information about the local extent, lesion size, and involvement of the neurovascular structures. Fibrosarcoma of bone typically has extraosseous extension.
Canale et al performed a retrospective review of MRI features in six cases of infantile fibrosarcoma (patient age range, 0-6 months). A well-circumscribed single mass was the most common finding (five patients), and all the tumors were on limbs. The initial tumor signal was isointense to muscle on T1-weighted images and hyperintense on T2-weighted images, with all tumors being well circumscribed and half of them containing internal fibrous septa.
In three patients, the internal signal was homogeneous; in the other three, it was heterogeneous. An intense enhancement was seen in the three contrast-enhanced images that were available: heterogeneous in two and homogeneous in one. There was osseous erosion observed in the patient with distant metastasis. The tumors in all cases disappeared with chemotherapy and limited surgery.
Bone scanning with technetium-99m is a very useful adjunct in the evaluation of tumor stage.
It aids in the detection of bone metastatic or polyostotic disease. For fibrosarcoma, bone scanning has largely been supplanted by MRI. The main limitation of bone scanning is that it often is nonspecific.
Some authors have suggested the use of gallium and ultrasound scans for diagnosis. At present, the value of these tests for staging of sarcomas remains limited.
Ultimately, the diagnosis of fibrosarcoma is made with tissue obtained from a biopsy. Biopsy should be thought of as the first step toward treatment, rather than the last step in diagnosis. Biopsy should always follow a full radiographic workup.
Biopsy is best performed by the treating surgeon because that physician will be responsible for any final tumor resection and reconstruction. In addition, it is best performed at a center where a team approach is used in treating these rare tumors. At such centers, groups of oncologists, pathologists, radiologists, and surgeons, all with a specific interest in these problems, often are present. This broad pool of experience contributes greatly to the interpretation of tests and to the ultimate treatment outcome.
Any biopsy performed must include an adequate volume of tissue. In centers with expert interpretation, core-needle biopsy or fine-needle aspiration may be acceptable.
The biopsy must be performed in a way that avoids compromising any planned surgical excision or reconstruction. It must not contaminate significant neurovascular structures.
Fibrosarcomas are tumors of malignant fibroblasts and collagen. They vary in histologic grade.
Well-differentiated forms have multiple plump fibroblasts with deeply staining nuclei in a rich collagen background. Intermediate-grade tumors have the typical herringbone pattern, showing the diagnostic parallel sheets of cells arranged in intertwining whorls (see the image below). A slight degree of cellular pleomorphism exists.
High-grade lesions are very cellular, with marked cellular atypia and mitotic activity. The matrix is sparse. No malignant osteoid formation should be present. Higher grades are extremely anaplastic and pleomorphic, with bizarre nuclei that bring to mind the histologic features of malignant fibrous histiocytoma. In fact, some pathologists believe that the division between malignant fibrous histiocytoma, high-grade osteosarcoma, and fibrosarcoma may be artificial.
Wojcik et al assessed clinicopathologic and immunohistochemical features of primary sclerosing epithelioid fibrosarcoma (SEF) in eight patients (median age, 52 years; range, 25-73 years). Tumors mostly involved long bones of the extremities, were predominantly lytic, and were poorly marginated. Histologically, six tumors had pure SEF morphology; two had hybrid SEF/low-grade fibromyxoid sarcoma morphology; one showed focal dystrophic mineralization (limited to areas of necrosis); and none showed the lacelike mineralization pattern typical of osteosarcoma.
The majority of the tumors (6/8) strongly expressed MUC4. All but one patient tested negative for SATB2; in that case, variable weak to moderate staining occurred in approximately 50% of nuclei. The authors concluded that the combination of morphology, MUC4 expression, and the absence of SATB2 expression was highly useful in helping to establish the correct diagnosis.
Several staging systems are used for tumors of the musculoskeletal system. The two most common systems are that of the Musculoskeletal Tumor Society and that of the American Joint Committee on Cancer. Both systems include histologic grade, tumor site, and presence or absence of metastasis. Other factors that may be important in staging are the size and depth of the tumor.
Laboratory studies generally are not helpful during the initial evaluation.
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