The detection of cancer at its early stages requires the analysis of new biomarkers that are specific to the tumor and have less background than conventional biomarkers. Nanoparticles released by tumors into circulation are an important source of new biomarkers that have the potential to be sensitive enough for early stage cancer detection. These nanoparticles include exosomes, which are secreted by tumor cells at higher levels than healthy cells, contain biomolecular cargo from the tumor cells themselves, and perform critical functions in carcinogenesis.