High 18 F-FDG and Low 68 Ga-FAPI-04 Activity in a Case of Eosinophilic Liver Infiltration Induced by Immune Checkpoint Inhibitor.

A 70-year-old man, who underwent radical surgery for left lower lung squamous cell carcinoma 4 years ago and received sintilimab therapy 3 months ago for suspected hilar lymph node metastasis, presented with multiple liver lesions detected by MRI. Laboratory tests showed abnormally elevated eosinophil count with 4.89×10 9 /L. 18 F-FDG PET/CT imaging demonstrated significantly high FDG-avid in the liver lesions, while 68 Ga-FAPI-04 PET/MRI imaging revealed slight FAPI uptake. Histopathological examination of the liver biopsy indicated chronic granulomatous inflammation with necrosis and a large number of eosinophils. Combining with these tests, eosinophilic liver infiltration induced by the immune checkpoint inhibitor was diagnosed.