Fluorodeoxyglucose uptake in absence of CT abnormality on PET-CT: What is it?

Figure 9 Muscular uptake. A 45-year-old woman with history of leiomyosarcoma had fluorodeoxyglucose positron emission tomography-computer tomography (PET-CT) for restaging. Axial PET-CT images of the pelvis show intense focal muscular uptake in the left gluteus maximus, gluteus minimus and obturator intermus, with no corresponding lesions on the CT (arrows). Two subsequent magnetic resonance images were unremarkable of the muscles.