<s>[INST] context: 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 reaction(onion skin) * Lesion may have both lytic and sclerotic regions * Extraosseous component is radiolucent with the same density of soft tissue. ref : maheswari 9th ed [/INST] question: 7 years old child presents with a lesion in upper tibia. X-ray shows radiolucent area with Codman's triangle and Sunray appearance. Diagnosis is- | options: A: Ewing sarcoma B: Osteosarcoma C: Osteoid osteoma D: Chondrosarcoma | answer: B </s>