A Case of Intense 18F-fluoroestradiol (18F-FES) Uptake in Hepatic Focal Nodular Hyperplasia

We report the first documented case of focal nodular hyperplasia (FNH) demonstrating intense uptake on 18 F-fluoroestradiol ( 18 F-FES) PET/CT. A 46-year-old premenopausal woman with newly diagnosed ER-positive invasive lobular breast cancer underwent whole-body 18 F-FES PET/CT, which incidentally revealed a 3-cm hepatic mass with uptake comparable to physiological liver activity. Multimodality imaging (MRI, dynamic CT, and Sonazoid ultrasonography) showed characteristic features of FNH, which remained stable for 4 years. This case demonstrates that FNH can exhibit marked FES uptake. Awareness of this benign cause of FES avidity is important to avoid misinterpreting hepatic FES-avid lesions as metastasis.