<prompt> Commonest bone malignancy is:OsteosarcomaChondrosarcomaEwing sarcomaSecondaries  <response>: Ans: D Secondaries Metastatic deposits in the bone are commoner than primary tumor. Of the primary bone malignancies, multiple myeloma is the commonest. Osteochondroma is the commonest benign tumor- Maheswari 3rd214METASTATIC BONE TUMORSCarcinomas often metastasize to the skeleton, and metastatic lesions are much more common than primary bone lesions in general orthopaedic practice.The five primary cancers with a strong propensity to metastasize to bone are those originating in the breast, prostate, lung., kidney, and thyroid.The axial skeleton, including the skull, thoracic spine, ribs, lumbar spine, and pelvis, is most commonly involved. The proximal long bones, particularly the humerus and femur, also are affected frequently. Acral distal metastases are uncommon0 and are almost always secondary to lung carcinoma when they do occur.The predilection of particular tumors for bone, and forparticular regions of specific bones, is thought to be caused by cytokines, local growth factors, or matrix components that attract and support growth of these lesions in spedfic areas. Lesions can be blastic breast, prostate, lytic breast, lung, myeloma, kidney, thyroid, or mixed breast, lung in radiographic appearance. Blastic or sclerotic lesions are less prone to pathologic fractures. Age predilection TumorAge range yrs AgeBenignMalignantOther 0-5 yrs child- Eosinophilic granuloma- Unicameral bone cyst rare- Leukemia- Metastatic neuroblastoma- Osteomyelitis- Stress fractureEosinophilic granuloma Ewings tumor1-155-15 6-18 yrsyoungadolescent- Unicameral bone cyst- Aneurysmal bone cyst- Eosinophilic granuloma- Enchondroma- Chondroblastoma- Chondromyxoid fibroma- Ewings sarcoma- Osteo sarcoma Non ossifying fibroma Fibrous cortical defect Simple unicameral bone cyst2-20 Aneurysmal hone cyst5-20 Osteogenic sarcoma5-20 Chondroblastoma Chondromyxoid fibroma5-2510-30 19-40 yrs adult- Osteoblastoma- Osteoclastoma- Eosnophilie granuloma- Ewings sarcoma Osteoid osteoma Osteoblastoma10-35 40 yrs middle aged old - Metastasis breast, lung, prostate, renal, thyroid, colon- Multiple myeloma- Lymphoma- Pagets disease- Hyperpara thyroidism- OsteomyelitisEnchondroma15-40 Osteoclastoma GCC20-40q ChondrosarcomaFibrosarcoma30-60q Lymphoma Multiple myelomaMetastasis50q 