18 F-FDG PET/CT Finding of Hepatocellular Carcinoma Mimicking Focal Fat Sparing in Severe Fatty Liver.

A 42-year-old man with progressive left arm pain underwent ¹⁸F-FDG PET/CT for evaluation of a suspected malignant humeral lesion. PET/CT revealed intense uptake in the left humerus but no other hypermetabolic foci. The liver demonstrated severe fatty infiltration (mean CT attenuation, -4 HU) with several nodules showing only mildly increased FDG uptake, initially interpreted as benign focal fat sparing (hepatic islands) given the patient's normal α-fetoprotein level and absence of hepatitis or alcohol history. Biopsy of the humeral lesion revealed metastatic carcinoma of hepatic origin, and subsequent liver biopsy confirmed moderately differentiated hepatocellular carcinoma (HCC). Awareness of this pitfall is essential to avoid overlooking HCC in the background of severe hepatic steatosis.