Association between intraosseous schwannoma occurrence and the position of the intraosseous nutrient vessel: A case report.

Intraosseous schwannoma is a rare benign bone tumor that originates from Schwann cells of the nerve sheath. The majority of intraosseous schwannomas arise in the mandible and sacrum, but an intraosseous schwannoma involving the ulna is described in the present case report. Radiologically, the current case presented as a well-defined lytic lesion, with a pathological fracture and no intralesional calcification, in the proximal metaphysis of the left ulna. Using magnetic resonance imaging, an intraosseous mass spreading out from the cortical defect was observed. The lesion appeared isointense to skeletal muscle on T1-weighted images, and hyperintense or heterogeneous on T2-weighted images. The differential diagnosis comprised benign bone tumors, including bone cyst, aneurysmal bone cyst, giant cell tumor and fibrous dysplasia. Based on the results of a needle biopsy, a schwannoma involving the ulnar bone was diagnosed, and tumor marginal resection followed by artificial bone grafting and fixation was performed. A total of one year subsequent to surgery, the patient exhibits no symptoms, and there is no evidence of disease recurrence.