<prompt> Please answer with one of the option in the bracket. Write reasoning in between . Write answer in between .Q:A 14-year-old boy is brought to the physician by his mother because of a 1-month history of pain in his right leg. His mother has been giving him ketorolac at night to improve his sleep, but the pain has not improved. Physical examination shows marked tenderness along the right mid-femur. An x-ray of the right lower extremity shows several lytic lesions in the diaphysis of the femur and a surrounding cortex covered by several layers of new bone. A biopsy of the right femur shows small round blue cells. Which of the following is the most likely diagnosis?? A: Ewing sarcoma, B: Chondroblastoma, C: Osteochondroma, D: Chondrosarcoma, E: Osteoid osteoma,  <response>: This is a clinical case about a 14-year-old boy with a 1-month history of right leg pain that is not improving with pain medication. The x-ray findings show lytic lesions in the right femur with reactive new bone formation. The biopsy shows small round blue cells. The key findings are the age of the patient 14 years old, lytic bone lesions with reactive new bone formation on x-ray, and small round blue cells on biopsy. This clinical presentation is most consistent with Ewing sarcoma, an aggressive malignant bone tumor that often arises in the long bones of children and adolescents. It can cause lytic bone lesions and a reactive new bone response. The small round blue cells on biopsy are characteristic of Ewing sarcoma.The other choices can be ruled out: Chondroblastoma and osteochondroma do not have the imaging or biopsy findings described. Chondrosarcoma is unlikely in a pediatric patient and would not show the small round blue cell pathology. Osteoid osteoma may cause reactive new bone formation but does not have the lytic lesions or cell pathology described.A: Ewing sarcoma 