Myofibrosarcoma of the bone: a clinicopathologic study

Area of Science:

• Orthopedic Oncology
• Soft Tissue Pathology
• Skeletal Neoplasms

Background:

• Myofibroblastic tumors represent a recently defined group of soft tissue neoplasms.
• While generally benign, myofibrosarcomas are considered their malignant counterparts.
• Bone involvement by myofibrosarcoma is rare, necessitating detailed clinicopathologic characterization.

Purpose of the Study:

• To describe the clinicopathologic and radiologic features of four bone myofibrosarcoma cases.
• To highlight distinctive histopathologic findings for differential diagnosis.
• To assess the clinical behavior and outcomes of this rare bone tumor.

Main Methods:

• Retrospective analysis of four cases of bone myofibrosarcoma.
• Review of clinical, radiologic, and histopathologic data.
• Immunohistochemical analysis using a panel of markers including vimentin, muscle actin, alpha-smooth muscle actin, calponin, desmin, and caldesmon.

Main Results:

• Four cases (3 female, 1 male; age 60-71) of bone myofibrosarcoma were identified, occurring in the distal femur and iliac bones.
• Radiologically, tumors presented as well-demarcated lytic lesions without periosteal reaction, with some extending into soft tissues.
• Histopathology revealed a mix of cellular fascicular areas and hypocellular fibrous zones, with focal necrosis and occasional pleomorphism. Immunohistochemistry showed positivity for myoid markers (actin, desmin, calponin) and vimentin, but negativity for high molecular weight caldesmon.

Conclusions:

• Bone myofibrosarcoma exhibits distinct clinicopathologic and radiologic features.
• Accurate histopathologic differentiation from other myoid tumors of bone is crucial.
• While wide resection can lead to excellent outcomes, the potential for distant metastasis exists, as evidenced by one fatal case.