Cancer that starts in bone tissue is called primary bone cancer, and the three most common types are osteosarcoma, chondrosarcoma, and Ewing sarcoma. Each name reflects the specific type of bone cell where the cancer originates. Primary bone cancer is rare, representing just 0.2% of all new cancer diagnoses in the United States, with an estimated 4,110 new cases expected in 2026.
Primary vs. Secondary Bone Cancer
The distinction between primary and secondary bone cancer is important because they are very different diseases. Primary bone cancer means the cancer originated in the bone itself. Secondary (or metastatic) bone cancer means a cancer that started somewhere else, like the breast, lung, or prostate, has spread to the bone. Secondary bone cancer is far more common, but it keeps the name of its original site. Breast cancer that spreads to the spine is still called breast cancer, not bone cancer.
Osteosarcoma
Osteosarcoma is the most common primary bone tumor. It develops in the cells that form new bone tissue, which is why it strikes most often during periods of rapid bone growth. The first peak in cases occurs during adolescence, when bones are growing quickly. A second, smaller peak appears in adults aged 60 and older, likely linked to other bone conditions that develop with age.
Osteosarcoma most frequently affects the long bones of the arms and legs, particularly around the knee and upper arm. Because it tends to appear in teenagers and young adults, it is one of the cancers parents and pediatricians watch for when a young person has persistent, unexplained bone pain or swelling near a joint.
Chondrosarcoma
Chondrosarcoma forms in cartilage-producing cells rather than bone-forming cells. It is a distinctly different disease from osteosarcoma in terms of who it affects and where it appears. Chondrosarcoma typically develops in adults between 40 and 70 years old, making it a cancer of middle and later life.
It tends to show up in the central skeleton: the pelvis, spine, and the upper portions of the long bones closer to the torso. Because cartilage tumors often grow slowly, some chondrosarcomas are low-grade and progress over years, while others are high-grade and more aggressive.
Ewing Sarcoma
Ewing sarcoma originates from a different cell type entirely. Rather than bone or cartilage cells, it arises from primitive cells in the bone marrow or cells related to nerve tissue. Like osteosarcoma, it is most common in the second decade of life, primarily affecting children and teenagers.
Ewing sarcoma favors different locations than osteosarcoma. It commonly develops in the pelvis, the middle shafts of long bones, the shoulder blade, and the ribs. This distribution means symptoms can sometimes mimic rib injuries, back pain, or other conditions before the correct diagnosis is made.
Rarer Types of Bone Cancer
Beyond the three major types, several less common cancers can start in bone. Chordoma is a slow-growing cancer that develops from remnants of the early spinal column tissue left over from embryonic development. It most often appears at the base of the spine (the sacrum) or the base of the skull. Chordomas account for roughly 40% of all primary tumors of the sacrum, and they typically occur in adults between 30 and 60, peaking around age 50.
Giant cell tumor of bone is another uncommon type. Despite its name, it is not always cancerous, but some forms are malignant or can become so. These tumors usually affect younger adults between 20 and 30 and tend to develop near the ends of long bones, particularly around the knee. In the sacrum, giant cell tumors are the second most common primary tumor, representing about 13% of cases there.
Malignant fibrous histiocytoma of bone is yet another rare subtype listed among primary bone cancers. It behaves similarly to osteosarcoma and tends to occur in adults rather than children.
What About Multiple Myeloma?
Multiple myeloma is sometimes confused with bone cancer because it causes significant bone damage and pain. However, myeloma is a blood cancer. The malignant cells are abnormal plasma cells that collect in the bone marrow and erode the outer layer of bone. Because the cancer begins in blood-forming cells rather than bone tissue, it is classified separately from primary bone cancers, even though its effects on the skeleton can be severe.
How Bone Cancer Is Staged
When a primary bone cancer is diagnosed, doctors determine its stage using two main systems. Both rely on similar factors: the grade of the tumor (how abnormal the cells look under a microscope), how far the tumor has extended, and whether it has spread to other parts of the body.
Grade is one of the most important factors. Low-grade bone cancers have cells that still resemble normal bone or cartilage cells and tend to grow more slowly. High-grade cancers look very abnormal and are more likely to grow and spread quickly. Beyond grade, staging considers whether the tumor is still contained within the bone or has broken through into surrounding tissue, and whether it has reached the lymph nodes or distant organs like the lungs.
These staging details help determine how aggressive the cancer is likely to be and guide decisions about treatment. A low-grade tumor still confined to the bone carries a very different outlook than a high-grade tumor that has spread beyond it.