Intraosseous neurilemmoma of the proximal ulna.
INTRODUCTION
Neurilemmoma is a benign nerve sheath neoplasm commonly located in the soft tissue. Intraosseous neurilemmoma is rare, constituting less than 1% of primary bone tumors.


PRESENTATION OF CASE
A 21 year-old woman was presented with left elbow pain of 1-month duration. Plain radiographs showed a well-defined, lytic and expansile lesion of the proximal ulna. Computed tomography revealed cortical destruction and soft tissue extension. Because the tissue of origin for the tumor was uncertain, an open biopsy was performed. The specimens demonstrated a benign spindle cell tumor suggestive of a neurilemmoma, similar to a soft tissue neurilemmoma. The diagnosis of intraosseous neurilemmoma was established. Marginal excision of the soft tissue component and curettage of the lesion in the bone were performed. After 3.5 years of follow up, there is no clinical or radiographic finding to suggest any recurrence.


DISCUSSION
The major site of intraosseous neurilemmoma is the mandible. Occurrence in the long bone is particularly rare. Only two cases of intraosseous neurilemmoma involving the bones around the elbow have been reported to our knowledge; these cases arose in the distal humerus. We describe the first case of intraosseous neurilemmoma of the proximal ulna of the left elbow. The recommended treatment is conservative resection and bone grafting, as malignant change is extremely rare.


CONCLUSION
Although very rare, intraosseous neurilemmoma should be taken under consideration in the differential diagnosis of painful, radiographically benign-appearing osseous tumor around the elbow.