A 16-year-old boy presents with a 3-month history of progressive knee pain and swelling. Plain radiographs show a metaphyseal lesion in the distal femur with a wide zone of transition, cortical destruction, and a mixed lytic-sclerotic pattern. MRI demonstrates a heterogeneous mass with areas of necrosis and hemorrhage. Regarding the imaging characteristics of osteosarcoma, all of the following are true EXCEPT: