Affiliation:
1. Orthopaedic Oncology Service, Department of Orthopaedic Surgery Massachusetts General Hospital, Harvard Medical School Boston Massachusetts USA
2. Division of Bone and Soft Tissue Pathology, Department of Pathology Massachusetts General Hospital, Harvard Medical School Boston Massachusetts USA
3. Division of Musculoskeletal Imaging & Intervention, Department of Radiology Massachusetts General Hospital, Harvard Medical School Boston Massachusetts USA
Abstract
Myositis ossificans, a benign tumor composed of spindle cells and osteoblasts, can clinically and radiologically mimic osteosarcoma. While recognition and accurate diagnosis of myositis ossificans can be a challenge, this is critical as it may allow a conservative surgical approach to maximize functional outcomes. Herein, we present a patient with surface myositis ossificans confirmed genetically by the presence of COL1A1::USP6 gene fusion, along with a literature review. Due to the enhanced visualization of the bone matrix, computed tomography (CT) imaging may be a superior imaging modality to magnetic resonance (MR) imaging. Staged biopsies with samples obtained from the periphery and center of the lesions may allow pathologists to discern the zonal distribution histologically. Furthermore, immunohistochemistry fluorescence in situ hybridization and molecular testing can aid in the distinction of myositis ossificans from mimics. Because of their resemblance to other bone tumors, these cases of myositis ossificans highlight the importance of a multidisciplinary approach integrating clinical, radiologic, and pathologic analysis and involving serial imaging, sampling, and judicious use of ancillary immunohistochemical and molecular testing.