Bone Tumor Imaging Patterns

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:

A 16-year-old boy presents with a 3-month history of progressive pain and swelling over the distal femur, just above the knee. On examination, there is a firm, fixed mass with overlying skin warmth. Plain radiographs show a mixed lytic and sclerotic lesion at the distal femoral metaphysis with cortical destruction and a wide zone of transition. There is a prominent sunburst pattern of periosteal reaction. MRI reveals a large soft tissue mass with heterogeneous signal intensity and areas of necrosis. Which is the most likely diagnosis?

A 65-year-old woman with a history of breast cancer (treated 8 years ago) presents with severe back pain and a pathological fracture of the L3 vertebral body. Plain radiographs show a lytic lesion with cortical destruction. Which imaging modality is most appropriate to assess the extent of spinal involvement and guide surgical planning?

Which radiological sign describes a bone tumor that has broken through the cortex and lifted the periosteum, creating a triangular area of new bone formation at the margin of the lesion?

A 35-year-old woman presents with a 6-month history of progressive pain and stiffness in the proximal humerus. On examination, there is mild limitation of shoulder abduction. Plain radiographs show a well-defined, sclerotic lesion in the proximal humeral metaphysis with a narrow zone of transition and a surrounding rim of sclerosis. There is no periosteal reaction or cortical destruction. CT imaging reveals internal calcification with a popcorn-like or chondroid appearance. MRI shows low-signal lesion with areas of high signal fat planes between the lesion and surrounding bone. Which is the most likely diagnosis?