Intrauterine accumulation of F-18 FDG during menstruation

A 45-year-old woman underwent a whole-body FDG PET study during her menstrual cycle. On PET images, a focal area of increased F-18 FDG accumulation resembling a solitary pelvic tumor was noticed above the urinary bladder. MR imaging confirmed that the focal area was within the uterine cavity. After the PET study, a gynecologic examination including cytology was performed, and it revealed no pathologic lesion in the uterus. Fourteen months later, a second PET study was performed in the absence of menstruation. The PET result was normal. It is considered that during menstruation, high F-18 FDG accumulation can be observed in the uterus, probably due to intrauterine hemorrhage.