Lymphangiogenesis within both the primary tumor and draining lymph nodes has recently received much attention, as these events appear to correlate with increased metastasis and poor prognosis. This project will focus on the specific role of macrophages in this process. The first goal is the development of in vivo imaging techniques, using magnetic resonance and bioluminescence imaging, that can measure lymphatic drainage and detect metastases in the sentinel lymph node. These techniques will be applied to novel animal models with increased macrophage recruitment to the tumor and with macrophage depletion. These studies may lead to novel macrophage-based strategies to decrease lymphatic metastasis.