Indeed: (1) the two tracers are markers of different targets in a tumor lesion: tumor stroma cells in one case, and properly tumor cells in the other; (2) lesions’ uptake reflects different biological mechanisms for each of them: stromal FAP expression and cancer glucose metabolism, respectively; (3) tumor cells generally account for less than 10% of the total cancer tissue, whereas the tumoral stroma accounts for all the rest. Here, FAP is linked to cancer.