The patient went on to have a biopsy.
Histology
The sections show a soft tissue proliferation composed of a myxoid spindle cell matrix within which are dispersed vascular structures of varying diameter and thicknesses, typical of a hemangioma. The spindle cell matrix is considered reactive and coexists with fresh hemorrhage and hemosiderin deposition. The lesional tissue is present at the biopsy margins.
Final diagnosis: intraosseus hemangioma.