Ewing Sarcoma

A 14-year-old girl with Ewing sarcoma of the right tibia (8 cm, intramedullary, no pulmonary metastases) has completed 6 weeks of neoadjuvant chemotherapy (VAC/IE). Repeat MRI shows 60% reduction in tumor volume and good response. The tumor is now deemed surgically resectable. What is the most appropriate next step in management?

A 16-year-old boy presents with a 3-month history of pain and swelling in the mid-shaft of the femur. Radiographs show a lytic lesion with a 'onion-skin' periosteal reaction and a wide zone of transition. MRI reveals a large soft tissue mass. Regarding the clinical and pathological features of Ewing sarcoma, all of the following are TRUE EXCEPT:

Which of the following is the most common site of origin for Ewing sarcoma?

A 16-year-old boy presents with a 3-month history of progressive pain and swelling in the left femur. He reports fever and weight loss over the past 6 weeks. On examination, there is a firm, warm swelling over the mid-shaft of the femur with restricted hip and knee movements. Laboratory investigations show an elevated ESR (78 mm/hr) and CRP (12 mg/dL). Plain radiographs reveal a mixed lytic and sclerotic lesion in the diaphysis with an onion-skin periosteal reaction. MRI shows a large soft tissue mass with marrow involvement. What is the most likely diagnosis?

A 16-year-old boy presents with a 3-month history of pain and swelling in the mid-shaft of the femur. Radiographs show a mixed lytic and sclerotic lesion with periosteal reaction. Which single feature best distinguishes Ewing sarcoma from osteosarcoma in this clinical scenario?