Spiculated periosteal reaction represents spicules of new bone forming along vascular channels and the fibrous bands that anchor tendons to bone (Sharpey fibers). A spiculated periosteal reaction signifies a rapid underlying process that prevents formation of new bone under the raised periosteum.
The orientation of the spicules reflects the direction of tumor growth. Spiculated periosteal reactions can be divided into subtypes based on the orientation of the spicules:
- osteoblastic metastasis