<s>[INST] context: 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 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. Refer Maheshwari 9th/e 239 [/INST] question: A child is diagnosed with Osteosarcoma based on Sunray appearance seen on x-ray. This is because of | options: A: Calcification along the periosteum B: Calcification along the blood vessels C: Perosteal reaction D: Soft tissue invasion | answer: C </s>