Focal nodular hyperplasia (FNH): a potential cause of false-positive positron emission tomography.

Positron emission tomography (PET) using F-18 fluorodeoxyglucose (FDG) has been proven to be a useful tool in the differential diagnosis of liver tumors. Focal nodular hyperplasia (FNH) is an uncommon benign liver lesion, which can be difficult to differentiate from other benign and malignant liver pathologies. FDG PET imaging usually shows uptake similar or even decreased compared to that of the normal liver. We describe a hypermetabolic FNH lesion in a patient with a history of breast cancer. Computed tomography scan, ultrasonography (US), and magnetic resonance imaging were negative. The lesion was resected, and histologic findings were consistent with FNH.