Ewing sarcoma is an aggressive malignant bone tumor seen in unlucky young subjects.

The multi-lamellated periosteal reaction (aka Onion skinning) is a hallmark of this tumor, though, it is not pathognomonic. 
Diaphyseal origin of the tumor and associated large soft tissue mass and / or swelling are characteristic features of Ewing sarcoma.

For this case, tissue biopsy confirmed Ewing sarcoma.