<prompt> Osteosarcoma can arise from:DiaphysisEpiphysisMetaphysisAll of the above  <response>: Ans. c Metaphysis. Ref. to Radiology Review Manual, 5th138; Essential orthopedics by Maheshwari 2nd218OSTEOSARCOMA It is 2nd most common 1deg malignant tumor of bone after multiple myeloma. Peak incidence in menl0-20 years of age. It has bimodal age distribution: 10-25 years and 60 years with M:F 3:2 to 2:1. Commonly found in the metaphysis of longbones, often around distal femur, proximal tibial region knee. Predisposing factors include Pagets disease of bone, bone infarcts, radiation, and familial retinoblastoma. Codmans triangle or sunburst pattern from elevation of periosteum on x-ray. MRI is preferred modality. Clearly defines marrow extent best on T1W1, vascular involvement and soft tissue component best on T2W1. Radionuclide bone scan NUC shows intensity increased activity on blood flow, blood pool, delayed images hypervascularity, new bone formation. Doughnut sign peripherally increased uptake with central photopenia on bone scan is a classical feature. Poor prognosis. Standard management: Preoperative chemotherapy followed by limb-sparing surgery followed by postoperative chemotherapy Sandwich Therapy. Rx:Osteosarcoma is radio- resistant; radiation therapy has no role in the routine management.Ewings sarcomaAnaplastic small blue cell malignant tumor. Most common in boys 15. Extremely aggressive with early mets, but responsive to chemotherapy. Characteristic onion-skin appearance in bone going out for Ewings and onion rings. Commonly appears in diaphysis of long bones, pelvis, scapula, and ribs. 11;22 translocation.ChondrosarcomaMalignant cartilaginous tumor. Most common in men aged 30-60. Usually located in pelvis, spine, scapula, humerus, tibia, or femur. May be of 1deg origin or from osteochondroma. Expansile glistening mass within the medullary cavity 