<prompt> An eight years old boy presents with progressive swelling around the knee joint of two months duration following mild trauma . Local examination reveals an irregular bony swelling over the upper end of tibia, with raised local temperature and of variable consistency and defined margins. The most likely diagnosis is -Giant cell tumourEwings sarcomaOsteogenic sarcomaSecondary metastasis  <response>: The clinical presentation in question can occur both in Ewings sarcoma and osteosarcoma.History of trivial traumaProgressive swellingRaised local temperatureVariable consistencyill defined margins.However, swelling is around the knee joint at upper end of tibia, which favours the diagnosis of osteosarcoma metaphyseal lesion.Ewings sarcoma usually occurs in the diaphysis of the bone middle of the shaft. 