Bone Tumors

A 13-year-old previously healthy boy presents to his pediatrician with a 6-week history of progressive, deep, aching pain in his right thigh. Over the past week, his parents have noticed a subtle, firm swelling in the same area. The pain is present at rest and often wakes him from sleep. He denies any significant trauma. He has had intermittent low-grade fevers over the past month. On examination, vital signs are normal except for a temperature of 37.8°C. There is a firm, tender, non-mobile mass palpable over the mid-diaphysis of his right femur, with slight overlying warmth. No erythema is present. Range of motion of the hip and knee is full but painful at extremes. Anteroposterior and lateral radiographs of the femur reveal a permeative, moth-eaten pattern of bony destruction in the diaphysis with a prominent, multi-layered 'onion skin' periosteal reaction.