Why is it important to identify a pathologic fracture prior to biopsy?

• A. Callus developing as result of pathologic fracture may be nondiagnostic for primary lesion and fracture callus may share a number of microscopic characteristics with osteosarcoma.
• B. Biopsy should be performed only after fracture has healed to avoid misdiagnosis.
• C. Pathologic fracture always indicates osteosarcoma; biopsy not needed.
• D. Fracture callus helps clearly identify the primary tumor on radiographs.

Answer: (A)

When a bone lesion has caused a pathologic fracture, healing tissue forms a fracture callus that can obscure the true tumor. This reparative tissue contains osteoid, woven bone, and inflammatory and fibrovascular components that can mimic malignant features, including those seen with osteosarcoma. If a biopsy samples the callus rather than the actual tumor, the specimen may be nondiagnostic for the primary lesion and could lead to misinterpretation. Recognizing a pathologic fracture beforehand guides sampling to areas away from the healing callus or even scheduling biopsy after some healing, so the histology more accurately reflects the underlying neoplasm. Imaging and histology must be correlated to avoid mistaking reparative tissue for malignancy.