What are the major causes for false positive FDG PET findings in cancer patients?
False-positive FDG PET findings may occur when there is active infection or noninfectious inflammation of any cause. For example, bacterial infection, mycobacterial infection, and sarcoidosis can all lead to increased FDG uptake in the body, potentially mimicking malignancy. Iatrogenic inflammation following radiation therapy often leads to increased FDG uptake, although it tends to be diffuse and geographic in distribution, often with linear margins. Also, increased FDG uptake can be seen in benign tumors, and physiologic increased FDG uptake can be seen in brown fat, bowel, and the genitourinary system.