Infiltration and migration of c-fms+ myeloid cells in the tumor microenvironment. c-fms+ myeloid cells migrate at the border of a late carcinoma, whereas migration within the tumor mass mostly occurs along blood vessels and in stromal patches. c-fms+ cells (green) are seen migrating at the border of the carcinoma (blue) in the bottom of the field, along c-fms+-dense tracks that penetrate into the tumor mass and along blood vessels inside the mass in an MMTV-PyMT;ACTB-ECFP;c-fms-EGFP mouse. Few of the c-fms+ cells that have infiltrated the carcinoma mass migrate. c-fms+ cells are also seen flowing through blood vessels inside the lesion (black areas on the surrounding background of blue cancer cells). From Egeblad et al. (2008) Dis. Model. Mech., 1 155-167.