Which feature supports absence of tumor and presence of periosteal reactive bone in this sample?

• A. Trabeculae are interconnected, thicker on one edge, and thinner immediately beneath the periosteum
• B. Uniform woven bone throughout with smooth margins
• C. Extensive endosteal destruction
• D. Massive osteolysis with no reactive bone

Answer: (A)

Periosteal reaction is the bone’s outward response to irritation or injury. When the periosteum is stimulated but the lesion is not neoplastic, new bone forms in an organized pattern along the outer surface, preserving cortex and showing a defined edge rather than aggressive destruction.

The described feature—trabeculae that are interconnected with thickening at the periosteal edge and thinning just beneath the periosteum—reflects this organized periosteal new bone formation. It implies a reactive rim of bone laid down by periosteal osteoblasts, consistent with absence of tumor invasion and presence of periosteal reactive bone.

Other patterns imply different pathology: extensive endosteal destruction or massive osteolysis point to aggressive lesions or tumors, while uniform woven bone with smooth margins could be seen in rapid healing but doesn’t specifically illustrate the outward periosteal reaction signal here.