To further confirm the presence of these HLMs at cellular resolution, whole tissue cross-sections of orthotopic murine MMTV-PyMT mammary tumors, livers, and spleens were stained by Prussian blue iron(IIII) and the general marker CD68 (Fig 2a), revealing iron(III)+ cells characterized as HLMs co-localized with CD68+ macrophages. The gene discussed is CD68; the disease is breast cancer.