<prompt> An 11year old boy presented with the complaints of pain in the right arm near the shoulder. X-ray examination revealed an expansile lytic lesion in the upper third of humerus. The most likely diagnosis is -Giant cell tumorUnicameral bone cystOsteochondromaParosteal osteosarcoma  <response>: Two most important differential diagnosis of expansile lytic lesion in proximal humerus and proximal femur in children are : -Simple bone cyst unicameral bone cystAneurysmal bone cystAmong these two, only unicameral bone cyst is there in options. Therefore, no further discussion is required. 