Which periosteal reaction is described as hair on end in Ewing sarcoma?

Which periosteal reaction is described as hair on end in Ewing sarcoma?

• A. Hair on end
• B. Onion-skin periosteal reaction
• C. Sunburst pattern
• D. Parallel periosteal reaction

Answer: (A)

The main idea is how aggressively the periosteum responds to an underlying lesion. Ewing sarcoma tends to provoke a very fast periosteal reaction, and one descriptive pattern for this rapid response is hair-on-end. This appearance comes from vertical, perpendicular spicules of new bone that shoot out from the cortex, giving a radiographic look reminiscent of hair standing on end. It reflects the tumor’s aggressive, rapid growth and the periosteum’s brisk activity in laying down bone in response. While onion-skin layering is another classic description for Ewing, the hair-on-end pattern specifically highlights those parallel, upright periosteal spicules. In contrast, a sunburst pattern indicates a chaotic, radiating push of bone typically seen with osteosarcoma, and a parallel periosteal reaction suggests a slower or healing process rather than an aggressive, rapid one.

The main idea is how aggressively the periosteum responds to an underlying lesion. Ewing sarcoma tends to provoke a very fast periosteal reaction, and one descriptive pattern for this rapid response is hair-on-end. This appearance comes from vertical, perpendicular spicules of new bone that shoot out from the cortex, giving a radiographic look reminiscent of hair standing on end. It reflects the tumor’s aggressive, rapid growth and the periosteum’s brisk activity in laying down bone in response.

While onion-skin layering is another classic description for Ewing, the hair-on-end pattern specifically highlights those parallel, upright periosteal spicules. In contrast, a sunburst pattern indicates a chaotic, radiating push of bone typically seen with osteosarcoma, and a parallel periosteal reaction suggests a slower or healing process rather than an aggressive, rapid one.