Tumor metastasis is a leading cause of cancer death. The metastatic switch marking the onset of metastatic dissemination corresponds to the acquisition of specific traits by tumor cells, including migration, invasion, and survival in the blood stream. Three main lines of evidence led us to hypothesize that metastasis is under metabolic control. First, PET with the glucose analog tracer -F-fluorodeoxyglucose (FDG) is routinely used for the clinical detection and imaging of tumor metastasis. This application is based on the observation that the vast majority of metastases trap far more glucose than normal tissues (with the exception of the brain), which has often been related to metabolic characteristics already acquired at the primary tumor site.