This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Tumors, Subject name: Orthopaedics
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 ill defined margins. The most likely diagnosis is - 
Select and explain. 
A. Giant cell tumour, B. Ewing's sarcoma, C. Osteogenic sarcoma, D. Secondary metastasis
C: Osteogenic sarcoma
Answer: C: Osteogenic sarcoma 
Explanation: OSTEOSARCOMA : Classification * PRIMARY or SECONDARY * PRIMARY OSTEOSARCOMAS (15 - 25 yrs) Conventional /classic osteosarcoma (high grade, intra medullar y) Low-grade intramedullary osteosarcoma Paraosteal osteosarcoma Periosteal osteosarcoma High-grade surface osteosarcoma Telangiectatic osteosarcoma, and Small cell osteosarcoma. * SECONDARY OSTEOSARCOMAS * Osteosarcoma occurring at the site of another disease process. * more common in >50 years of age most commonly a/w premalignant condition like - Paget disease - Previous radiation treatment - endochondromatosis - Fibrous dysplasia - Osteochondromas - Osteogenesis imperfecta Clinical Presentation * Pain- progressive pain paicularly with activity. * Swelling - Palpable mass in the region of metaphysis. - skin over the swelling shiny with prominent veins. - swelling may be warm & tender. * Decreased range of motion of the involved joint. * Lymphadenopathy - unusual focal & regional lymph node involvement. * Respiratory finding - late stage with lung metastasis. * Fever & night sweats are rare. Treatment Radioloical staging Biopsy to confirm diagnosis Preo perat ivhemotherapy Repeat radiological staging (access chemo response, finalize surgical treatmeni Ian) Surgical resecting with wide margin Reconstruction using one of many techniques Post op chemo based on preop response ref : maheswari 9th ed