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

Figure 11 Uptake representing esophageal cancer. A 49-year-old man with history of retromolar carcinoma had fluorodeoxyglucose positron emission tomography-computer tomography (PET-CT) for restaging. Axial (A) and sagittal (B) PET-CT images show a focus in the mid esophagus at the subcarinal level (arrows), without a visible lesion or evident wall thickening on the integrated CT. Subsequent contrast CT was negative as well. An endoscopic biopsy revealed squamous cell carcinoma.