Fibrosarcoma Workup

• Laboratory studies generally are not helpful during the initial evaluation.

• Plain radiographs

  • Plain radiographs of the involved anatomic region are needed to evaluate for primary or secondary involvement of bone. 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.
• Computed tomography (CT) scans

  • For sarcomas arising in bone, CT scanning 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 scanning of the chest may be appropriate. CT scanning is very sensitive for metastatic disease.
• Magnetic resonance imaging (MRI) scans

  • MRI may be the best modality overall for examining soft-tissue masses and for detecting the intraosseous and extraosseous extent of many bony sarcomas.^[4]
  • MRI is useful in providing information about the local extent, lesion size, and involvement of the neurovascular structures. Fibrosarcoma of bone typically has extraosseous extension.
• Bone scans

  • Bone scanning using technetium-99m is a very useful adjunct in the evaluation of tumor stage.
  • Bone scanning aids in the detection of bone metastatic or polyostotic disease.
  • For fibrosarcoma, bone scanning has been mostly supplanted by MRI. The limitation with bone scanning is that it often is nonspecific.
• Other

  • Some authors have suggested the use of gallium and ultrasound scans for diagnosis. To date, the value of these tests for staging of sarcomas remains limited.

• Biopsy

  • 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.
  • Biopsy 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. 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.

Several staging systems are used for tumors of the musculoskeletal system. The 2 most common systems are those of the Musculoskeletal Tumor Society and 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.