What is the most common primary malignant tumor of bone?

The most common primary malignant tumor of bone is actually osteosarcoma, especially in adolescents and young adults. Osteosarcoma typically arises in the metaphysis of long bones and is often associated with rapid growth. Although multiple myeloma is a notable malignancy, it is not classified as a primary bone tumor; rather, it is a hematologic malignancy that primarily affects plasma cells and can lead to bone lesions but originates in the bone marrow.

Chondrosarcoma and Ewing's sarcoma are also primary malignant bone tumors but are less common than osteosarcoma. Chondrosarcoma usually arises in cartilage-forming tissues and is more prevalent in older adults. Ewing's sarcoma, mostly seen in children and adolescents, is another rare tumor that can arise from the bone or soft tissues.

Understanding these classifications is crucial for differentiating the types of bone tumors and their respective epidemiologies. In essence, while multiple myeloma is significant in the realm of bone pathologies due to its effects on bone integrity, it does not represent a primary malignant tumor of bone itself.