The three most common primary cancers of bones and joints are osteosarcoma, Ewing sarcoma, and chondrosarcoma. Of the three, chondrosarcoma has the best prognosis. The ages at which these cancers most often occur vary. Osteosarcoma, a malignant bone tissue tumor commonly found near the growing end of the long bones, is the most common, and occurs most frequently in teens and young adults. Ewing sarcoma, a tumor often located in the shaft of long bones and in the pelvic bones, occurs most frequently in children and youth. Chondrosarcoma, a sarcoma of malignant cartilage cells, often occurs as the result of malignant degeneration of pre-existing cartilage cells within bone, including chondromas (a benign tumor), and is primarily found among older adults. However, the vast majority of chondromas never undergo malignant change; therefore, the routine resection of benign chondromas is unwarranted.
Of these three, Ewing sarcoma is generally considered to have the worst prognosis, followed by osteosarcoma. However, this perception is largely due to the greater tendency for osteosarcomas to present as high-grade tumors and for chondrosarcomas to present as low-grade tumors. When analyzed by stage, a recent survivorship analysis revealed similar survivorship rates for low-grade chondrosarcoma compared to low-grade osteosarcoma, and similar survivorship rates for high-grade chondrosarcoma when compared to high grade osteosarcoma. By definition, all cases of Ewing sarcoma are high-grade, the most aggressive category of cancer, with full potential to metastasize and bring about death. Approximately 6% to 20% of osteosarcomas are of lower grade; chondrosarcoma has a higher proportion of low-grade cases than these other two bone and joint cancers.
The fourth common “primary” cancer of the bone is myeloma, a malignant primary tumor of the bone marrow formed from a type of bone marrow cells called plasma cells (the cells that manufacture antibodies). This cancer and usually involves multiple bones simultaneously. The isolated single-bone version of myeloma is called plasmacytoma, but virtually all cases of isolated plasmacytoma evolve into full-fledged multiple myeloma within 5 to 10 years after diagnosis of the plasmacytoma. Like leukemia and lymphoma, myeloma is more properly considered a primary cancer of the hematopoietic bone marrow. Unlike leukemia, however, myeloma typically causes extensive changes or damage to the bone structure itself, causing fractures, pain, and hypercalcemia. Because of the associated bone destruction, myeloma is generally included in analysis of bone cancers; however, leukemia and lymphomas generally are not considered primary bone cancers, presumably because of the lower likelihood of structural bone destruction and associated complications. Non-Hodgkin’s lymphomas, however, warrant some consideration due to the frequency of bone destruction and pathological fractures requiring operative intervention.