Midline cyst of the prostate mimicking malignancy on FDG PET/CT.

A 58-years-old man underwent F-18 FDG PET/CT for health screening. F-18 FDG PET/CT revealed a focal, round, and 1.5 cm-sized hypermetabolic lesion at midline of the prostate. The lesion was suspected as a urinary activity or malignancy. On the review of medical records, it was found that the patient had undergone contrast-enhanced abdominal CT scan 1 day before PET/CT examination. On the attenuation-uncorrected image, the prostatic lesion was still evident. The lesion was considered as a midline cyst of prostate, communicating with urethra. It is suggested that radioactive urine remained in midline cyst resulting in the focal hypermetabolic lesion.