FAPI-Negative but FDG-Avid Hepatocellular Carcinoma With Extensive Steatosis

An 80-year-old man underwent 68 Ga-FAPI and 18 F-FDG PET scans to determine the nature of a liver mass that exhibited high FDG uptake unexpectedly but was FAPI-negative. Postoperative pathology confirmed atypical hepatocellular carcinoma (HCC) with extensive steatosis. Intratumoral steatosis is uncommon in large lesions, and extensive steatosis may mask tumor characteristics, which increases diagnostic complexity. This unusual case provides novel insights into the clinical application of FDG and FAPI PET and highlights the importance of recognizing FAPI false-negatives, thereby contributing to clinical practice.