FAP and cancer: MAFs were identified with a commonly used cancer-associated fibroblast marker fibroblast activation protein (FAP), while macrophages were detected using ionized calcium binding adapter molecule 1, IBA-1 (also known as allograft inflammatory factor 1, AIF1), a highly specific marker used to detect tumor-associated macrophages [27,28] FAP-positive MAFs were readily identified within the cancer stroma, and interestingly, the majority of these stromal cells were surrounded by macrophages (Figure 4).