EPCAM and cancer: The imaging probes in this study were chosen to highlight three main compartments in the tumor (figure 1B): cancer cells via an epithelial antigen (CD326, EpCAM commonly used to detect circulating cancer cells and overexpressed on a wide variety of epithelial cancers[17]), functional supporting microvasculature (a probe with prolonged distribution in the plasma volume), and stromal tissue (easily targeted innate immune cells, such as the CD11b pool).