Intraosseous schwannoma of distal femur: A case report

INTRODUCTION AND IMPORTANCE: Intraosseous schwannoma is a rare benign tumor, which mostly occurred in head and neck region. In this report we aimed to describe a unique case of intraosseous schwannoma in the distal femur without any other clinical finding aside from pain and tenderness. CASE PRESENTATION: 19-year-old female presented with persistent pain on her left thigh for 4 years. Aside from tenderness on her left thigh, her physical examination was unremarkable. Plain radiographic of left femur showed a small geographic osteolytic cortical lesion with sclerotic rim in the distal region. Further evaluation with MRI showed eccentric lytic lesion with an isointense signal on T1-weighted images and a hyperintense signals on T2-weighted images. Patient then temporarily diagnosed with osteoblastoma. Because there were no signs of malignancy, the patient underwent a curettage of the mass followed by synthetic bone graft application. Histopathological findings were consistent for schwannoma. Further immunohistochemical examination showed positive S100 staining, confirming the final diagnosis of intraosseous schwannoma. There were no signs of early complication on 3 months post-operation. The patient was further scheduled for follow up on 6 months and then routinely every year post-operation to evaluate any signs of complication or recurrence. CLINICAL DISCUSSION: It is difficult to make an accurate initial diagnosis of intraosseous schwannomas. Because the clinical presentation was most likely not specific as such in this case and there many other tumors of the bone with similar radiographic finding which are more common. Curettage of the mass followed by synthetic bone graft application was performed as there were no sign of malignancy making more invasive option deemed to cause more harm than good to the patient. CONCLUSION: The possibility of intraosseous schwannoma should have been taken under consideration in the differential diagnosis of osteolytic lesion with pain in long bone.