CD68 and neoplasm: Tumor tissue microarrays were also stained by multi-parameter immunofluorescence for Arg1 and other immune cell markers, and we found that Arg1 was more frequently associated with the granulocytic marker CD15 than with the macrophage marker CD68 (Fig. 8e), and in some cases, striking co-localization between Arg1 and CD15 was observed (Fig. 8f).