Magnetic Particle Imaging (MPI) is emerging as a specific, quantitative and sensitive cellular imaging technique. MPI directly detects a SPIO tracer as positive contrast, and this signal is linearly quantifiable with zero tissue attenuation. Because of this, MPI is well suited for in vivo cell tracking to image tumor associated macrophages (TAMs). TAM content can be used as a biomarker to predict tumor growth and metastatic potential. Mice bearing 4T1 and 168FARN tumors were imaged post intravenous SPIO injection to investigate for the first time, the application of MRI and MPI to differentiate between murine cancer models with varying metastatic potentials.