In osteosarcoma, is reactive bone present along with tumor bone?

• A. Yes, reactive bone may be present between tumor trabeculae if cortex breached
• B. No, reactive bone is never present
• C. Reactive bone is always present but not tumor bone
• D. Reactive bone is only found in slow-growing lesions

Answer: (A)

Osteosarcoma often shows a mix of tumor bone (osteoid produced by malignant osteoblasts) and reactive bone formed by the surrounding normal bone in response to the tumor. When the cortex is breached by the tumor, the periosteum can react by laying down new bone, resulting in reactive bone appearing between tumor trabeculae. This explains why reactive bone may be present alongside tumor bone. It’s not obligatory—some cases have minimal periosteal reaction—but the possibility exists. The other statements aren’t correct because reactive bone can occur, it isn’t guaranteed to be present in every case, and it isn’t limited to slow-growing lesions.