Aggressive Appearance of Non-Ossifying Fibroma with Pathologic Fracture: A Case Report

: An 11-year-old boy presented with a lytic lesion in the proximal humeral metaphysis. In spite of an aggressively reactive appearance on plain radiography and MR imaging, this lesion proved to be a non-ossifying fibroma. Fracture of the cortical shell probably contributed to the relatively wide zone of transition and periosteal reaction on plain radiography and the reactive change on MR imaging.