What are the major causes for false negative FDG PET findings in cancer patients?
False-negative FDG PET findings may occur when there is low tumor metabolic activity, such as with lepidic-predominant adenocarcinomas (minimally invasive or in situ), mucinous adenocarcinomas, and carcinoid tumors, or when the lesions are small in size due to the limitations of spatial resolution of PET. However, observation of no or minimal levels of FDG uptake within a tumor is useful information, because lower levels of FDG uptake generally reflect a more indolent tumor biology and portend a more favorable clinical outcome. False-negative findings may also occur in tissues where there is a high background level of FDG uptake such as in the brain, bowel, or urologic system.
