18 F-FDG Outperforms 18 F-FAPI-04 in Detecting Primary Splenic Angiosarcoma and Its Metastatic Lesions in Liver.

A few case reports show FAPI PET may be superior to FDG PET in evaluating angiosarcoma. We describe FDG PET/CT, delayed abdominal FDG PET/MRI, and 18 F-FAPI-04 PET/CT findings in a case of primary splenic angiosarcoma with diffuse hepatic metastases. In this case, FDG PET was superior to FAPI PET in evaluating the primary and metastatic tumors. FDG PET showed much higher activity in the primary splenic tumors compared with 18 F-FAPI-04 PET. FDG PET identified the hepatic metastases due to increased activity, which was missed on 18 F-FAPI-04 PET.