Periosteal bone formation in slow-growing vs fast-growing lesions: which statement is true?

• A. Slow-growing: continuous along cortex; cortex may appear thickened; thick interconnecting trabeculae merge with cortex
• B. Slow-growing: interrupted; long thin spicules of woven bone predominate
• C. Both show identical patterns
• D. Periosteal bone formation is absent in slow-growing lesions

Answer: (A)

Periosteal bone formation reflects how quickly a lesion expands: slow growth allows orderly, continuous deposition along the periosteum, while rapid growth produces disorganized, interrupted bone with spicules.

The true statement aligns with the slow-growing pattern: continuous periosteal reaction along the cortex, with the cortex appearing thickened and thick interconnecting trabeculae merging with the existing cortex. This reflects steady osteoblastic apposition that preserves a more solid, integrated periosteal response.

The other options don’t fit this scenario. An interrupted, long thin spicules pattern is more typical of rapid growth, not slow. Saying patterns are identical ignores the well-recognized difference in periosteal reactions between slow and fast lesions. Claiming periosteal formation is absent in slow-growing lesions is incorrect because slow-growing lesions still elicit a periosteal response, just a more solid one.

So the described continuous, cortex-merging periosteal reaction best characterizes slow-growing lesions.