Exosomes are naturally occurring biological nanovesicles utilized by tumors to communicate signals to local and remote cells and tissues. Melanoma exosomes can incite a proangiogenic signaling program capable of remodeling tissue matrices. In this study, we show exosome-mediated conditioning of lymph nodes and define microanatomic responses that license metastasis of melanoma cells. Homing of melanoma exosomes to sentinel lymph nodes imposes synchronized molecular signals that effect melanoma cell recruitment, extracellular matrix deposition, and vascular proliferation in the lymph nodes. Our findings highlight the pathophysiologic role and mechanisms of an exosome-mediated process of microanatomic niche preparation that facilitates lymphatic metastasis by cancer cells. Cancer Res; 71(11); 3792-801. Ó2011 AACR.