A 7 year old boy is taken to a physician because he has developed pain in his right hip. On physical examination, the physician feels a large mass near the iliac crest. Plain x-ray films demonstrate a large lytic lesion of the ilium. MRI studies show that the tumor appears to arise in the bone, but extends into the adjacent soft tissues. A large incisional biopsy demonstrates a tumor composed of sheets of small, round, blue cells. Which of the following is the most common bone to be affected by this tumor?
High-Yield Explanation
While any bone can be affected by Ewing sarcoma, the most common site is the diaphysis of the femur. Other common sites include the flat bones of the pelvis and the tibia. The other bones listed in the choices are not as common sites of involvement.