What is the most common primary malignancy of bone?

Osteosarcoma is the most common primary malignancy of bone, predominantly affecting adolescents and young adults. It typically arises in the metaphysis of long bones, particularly around the knee. The tumor is characterized by the production of osteoid or immature bone. It is important to recognize that while osteosarcoma is specifically a malignant bone tumor, other conditions listed, such as osteomalacia and osteomyelitis, refer to non-malignant processes. Osteomalacia involves the softening of the bones due to vitamin D deficiency and is not a cancer, while osteomyelitis is an infection of the bone.

Multiple myeloma, although it does involve the skeletal system and is classified as a hematologic malignancy, originates from plasma cells in the bone marrow and is considered a secondary malignancy when looking strictly at bone. Thus, osteosarcoma is distinguished as the primary malignancy of bone due to its nature, typical presentation, and demographic affected.