This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bone Tumour, Subject name: Orthopaedics
[{'content': 'The bone tumor seen in children with characteristic "onion-peel" periosteal reaction is? \nSelect and explain. \nA. Osteosarcoma, B. Giant cell tumor, C. Ewings sarcoma, D. Osteoid osteoma', 'role': 'user'}, {'content': 'Answer: C \nExplanation: ANSWER: (C) Ewing\'s sarcomaREF: Apley\'s system of orthopaedics 8\'h edition page 190, Tureks orthopaedics 6th edition page 307Repeat from June 2008EWING\'S SARCOMA:Highly malignant, undifferentiated peripheral primitive neuro ectodermal tumor (PEN)Most common site is diaphysis of femurCommon in 10-20 year old maleHistopathology shows round cells containing glycogen and reticulin; PAS positive and diastase digestable80-95% tumors possess translocation; t(ll; 22)X Ray reveals laminated periosteal new bone formation also known as "Onion peel appearance"', 'role': 'assistant'}]