ThahirKhan a 15-year-old boy presents with fever and pain in the right lower thigh. The pain has been ongoing for the past one month. On examination, there is a 2 cm by 2 cm mass at the lower third of his thigh which is red, warm, and tender. An X-ray shows bone destruction with overlying onion-skin layers of periosteal bone formation and a soft tissue mass. What is the SINGLE most likely diagnosis?