Isolated Skull Metastasis With Unusual Spiculated Periosteal Reaction From Rectal Cancer Resembling Osteosarcoma on FDG PET/CT

We describe FDG PET/CT findings in a case of isolated skull metastasis with spiculated periosteal reaction from rectal mucinous adenocarcinoma 8 years after proctectomy. The skull metastasis showed heterogeneous FDG uptake and multiple short spicules of bone producing the sunburst appearance resembling primary osteosarcoma or Ewing sarcoma. Familiarity with this atypical imaging appearance of the bone metastasis from rectal cancer may be helpful for the diagnosis and differential diagnosis.