Cyclic dinucleotides injected into tumors result in rapid hemorrhagic necrosis by activating the sensor STING. To examine expression of STING in the tumor environment, Panc02 pancreatic adenocarcinoma tumors grown in immune competent mice were stained for the macrophage marker F4/80 (red), STING (green), and the DAPI nuclear counterstain (blue). Both the cancer cells and the tumor stroma, including F4/80⁺ tumor macrophages, expressed STING; however, in STING^−/− mice, cyclic dinucleotides had no effect, indicating that it is the stromal rather than cancer expression of STING that mediates this effect. For details, see article by Baird and colleagues on page 50.