<prompt> A child is diagnosed with Osteosarcoma based on Sunray appearance seen on x-ray. This is because ofCalcification along the periosteumCalcification along the blood vesselsPerosteal reactionSoft tissue invasion  <response>: Sunray appearance is a typical type of Periosteal reaction along Sharpeys fibres OSTEOSARCOMA Highly malignant tumor arising from primitive mesenchymal bone-forming cells. Histologic hallmark is production of malignant osteoid. Mc histological form of primary bone cancer . A most common primary malignant bone tumor after Etiology Rapid bone growth - adolescence growth spu in the metaphyseal area near the growth plate. Radiation exposure - mostly causes secondary forms. Genetic predisposition : - hereditary form of retinoblastoma RB gene mutation - Li-Fraumeni syndrome p53 gene mutation - Rothmund - Thomson syndrome autosomal recessive Paget;s disease of bone - mostly secondary forms. 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 aw 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. Refer Maheshwari 9the 239 