Osteoblastoma of the Radial Shaft Mimicking Parosteal Osteosarcoma: A Case Report.

INTRODUCTION: Osteoblastoma is a rare benign osteogenic tumor accounting for approximately 1% of primary bone tumors. Involvement of the radial shaft is uncommon and may pose a diagnostic challenge because of overlapping radiological and histopathological features with surface osteosarcomas. We report a rare case of radial shaft osteoblastoma initially suspected to be parosteal osteosarcoma and managed with wide excision and biological reconstruction.

CASE REPORT: A 17-year-old male presented with progressive pain and swelling over the middle third of the right forearm for the preceding 6 months. Radiographs and magnetic resonance imaging demonstrated a surface-based lesion involving the radial shaft with aggressive radiological features. Core biopsy was suggestive of parosteal osteosarcoma. Due to the clinicoradiological suspicion of malignancy, wide excision of the involved radial segment was performed. Reconstruction was achieved using an ipsilateral non-vascularized fibular autograft stabilized with plate fixation. The pronator quadratus was excised en bloc with the lesion, and pronator teres was reattached to the fibular graft using a 2.8-mm suture anchor. Histopathological examination of the excised specimen demonstrated histomorphological features of a benign osteogenic tumor consistent with osteoblastoma, with no nuclear evidence of malignancy. Follow-up demonstrated satisfactory function and no evidence of recurrence.

CONCLUSION: Radial shaft osteoblastoma may mimic parosteal osteosarcoma clinically, radiologically, and on biopsy. Definitive diagnosis may require examination of the entire excised specimen. Biological reconstruction with ipsilateral fibular autograft can provide satisfactory functional outcomes.