<prompt> All of the following are true about Ewings sarcoma, EXCEPTResponds well to radiotherapyGrows in diaphysis of long bonesCommon in 4th decadeHas onion peel appearance on radiograph  <response>: C Common in 4th decade Ewing sarcoma, a highly malignant primary bone tumor. The tumor is derived from red bone marrow. Most frequently, it is observed in children and adolescents aged 4-15 years and rarely develops in adults older than 30 years. Ewing sarcoma is the second most common malignant bone tumor in young patients, and it is the most lethal bone tumor. Typically, the periosteal reaction and new bone formation with an onionskin appearance may suggest the diagnosis of E wing sarcoma. It is highly radiosensitive and it melts like ice but only to recur at a later date. 