Classification
Bone tumors may be classified as "primary tumors", which originate in bone or from bone-derived cells and tissues, and "secondary tumors" which originate in other sites and spread (metastasize) to the skeleton. Carcinomas of the prostate, breasts, lungs, thyroid & kidneys are the primary carcinomas that most commonly metastasize to the bone. Secondary malignant bone tumors are estimated to be 50 to 100 times as common as primary bone cancers.
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