<prompt> A 15-year-old boy is injured while playing cricket. X-rays of the leg rule out of a possible fracture. The radiologist repos the boy has an evidence of aggressive bone tumor with both bone destruction and soft tissue mass. The bone biopsy reveals a bone cancer with neural differentiation. Which of the following is the most likely diagnosis?ChondrablastomaEwings sarcomaNeuroblastomaOsteosarcoma  <response>: synol sarcoma : Clinical presentation Symptoms Local pain- universal complaint- intermittent, mild at first increase in severity with time worse at night Pain may be accompanied by paresthesia in pelvic or veebral tumors Conservative treatment of pain can delay the diagnosis for weeks to months Swelling- rapidly growing and painful, tense, elastic, hard with local raise of temperature. Not palpable if it is deep seated. Periods of remission can be present Few cases present with pathological fractures Weight loss, fatigue, intermittent pyrexia Signs Palpable tender mass with prominent veins Fever, erythema and swelling Joints and neurological manifestation, joint effusion with limited mobility Paralysis and root pain if spine involved Plain Radiography Presents as extensive diaphyseal lesion At midshaft of the long bone, the coex displays increased density, extending externally as periosteal new bone, forming multiple thin parallel layers giving ;onion peel appearence; Periosteal reactions may also have codmans triangle- lifting of periosteum from the bone. Ewing sarcoma appears as ill defined, permeative, focally moth eaten, destructive intramedullary lesion accompanied by a periosteal reactiononion skin Lesion may have both lytic and sclerotic regions Extraosseous component is radiolucent with the same density of soft tissue. ref : maheswari 9th ed 