Bone Cancer is classified into two types. Primary Bone Cancer, which is rare, and the more common Secondary Bone Cancer. Secondary Cancer is a result of another type of cancer spreading (metastasize) to the bones. Sadly, Osteosarcoma and Ewing are both forms of Primary Bone Cancer that occur more often in children than adults. Sarcomas are malignant tumors that affect the bones as well as other areas of the body.