Exosomes, small (30-150nm) extracellular vesicles of endocytic origin, are present in all body fluids of cancer patients. Tumor-derived exosomes, TEX, emerge as potentially promising non-invasive biomarkers of tumor progression and of immune cell dysfunction in cancer. Exosomes isolated from plasma by size exclusion chromatography can be fractionated into TEX and non-TEX by immune capture on beads. Profiling of molecular and genetic contents of TEX shows that levels if immunosuppressive proteins, such as PD-L1, carried by TEX associate with disease progression. The data suggest that TEX have a to serve as tumor surrogates, while immune cell-derived exosomes might serve as biomarkers of immune dysfunction in cancer.