Which of the following is a primary malignant tumor of the bone?

• A. Enchondroma
• B. Leiomyoma
• C. Lipoma
• D. Osteosarcoma

Answer: (D)

A primary malignant tumor of bone is one that originates in bone tissue itself, typically from bone-forming cells. Osteosarcoma fits this description because it arises from osteoblasts and produces osteoid matrix, making it a malignant cancer that starts in bone. It’s classically associated with the metaphysis of long bones in adolescents and young adults and can show aggressive growth with periosteal reactions on imaging. The other options are not bone cancers: enchondroma is a benign cartilaginous tumor within bone; leiomyoma is a benign smooth muscle tumor usually in soft tissue; lipoma is a benign tumor of fat tissue. Therefore, osteosarcoma is the correct choice.