Abnormal Fluorodeoxyglucose Uptake in Lung without Structural Abnormality on Computed Tomography

Fluorodeoxyglucose (FDG) positron emission tomography-computed tomography (PET-CT) is a useful proven imaging modality in the management of many types of cancers. It is being used at various stages of treatment of cancer. Knowledge regarding the physiological biodistribution and false-positive findings should be kept in mind for correct interpretation. Pulmonary FDG uptake can be due to different causes such as infection, inflammation, and metastases which are invariably associated with structural abnormality on CT. In rare circumstances, there can be a focus of FDG uptake in the lung with no corresponding structural abnormality which might be due to an inflammatory vascular microthrombus or due to iatrogenic microembolism caused during the injection of radiotracer. It is important to be aware of this as it can cause difficulty in interpreting the scan and can lead to false-positive findings. It also highlights the importance of hybrid imaging in the form of PET-CT as there is a definite possibility of misinterpreting this as a site of metastasis in a known carcinoma patient if there was no corresponding CT image.