Bone Tumors — Ewing

A 16-year-old girl presents with a 2-month history of pain in the right tibia and a palpable mass. She has had intermittent fever and night sweats. Plain radiographs show a mixed lytic and sclerotic lesion in the mid-shaft of the tibia with a "mottled" appearance and aggressive periosteal reaction. A bone biopsy is performed. Which histological finding would be most consistent with the suspected diagnosis?

Which chromosomal translocation is pathognomonic for Ewing sarcoma?

A 14-year-old boy from rural India presents with a 3-month history of progressive pain and swelling of the left femur. On examination, there is a firm, warm swelling over the mid-shaft of the femur with overlying skin erythema. He reports fever on and off and has lost 2 kg of weight. Laboratory investigations show WBC 12,500/μL, ESR 45 mm/hr, and CRP 8 mg/dL. Plain radiographs reveal a mixed lytic and sclerotic lesion in the diaphysis of the femur with periosteal reaction and a "onion-skin" pattern. MRI shows a large soft tissue mass with heterogeneous signal intensity. Which is the most likely diagnosis?

Ewing sarcoma typically arises in which anatomical location within the femur?