Which statement is NOT a feature of tumor bone?

• A. Trabeculae interconnected with mature lamellar bone
• B. Intertrabecular spaces filled with pleomorphic mesenchymal cells
• C. Frequent and often atypical mitoses
• D. Not lined by a single layer of plump osteoblasts

Answer: (A)

Tumor bone forms in a disorganized, immature way driven by malignant cells, so its architecture differs from normal bone. Instead of networks of mature lamellar trabeculae, tumor bone often shows irregular, woven bone or osteoid laid down in a haphazard pattern by proliferating malignant cells. The spaces between the trabeculae are typically filled with pleomorphic mesenchymal cells, and frequent, sometimes atypical mitoses reflect the malignant nature. The lining of bone trabeculae is not a uniform single layer of plump osteoblasts as seen in normal bone formation. Because of this mismatch with normal mature lamellar bone, the description of trabeculae interconnected with mature lamellar bone is not a feature of tumor bone.