“Onion skin,” which doctors call lamellated periosteal reaction, occurs when multiple layers of bone form in a concentric circle around the outer surface of the bone. It can occur with Ewing sarcoma.

Ewing sarcoma bone tumors have an onion-skin appearance on imaging scans. This happens because the tumors stimulate the growth of a membrane that surrounds the bones. Ewing sarcoma is a bone cancer ...