Cancer exosomes that carry specific molecules such as, PD-L1, CD63, Caveloin-1, MIA, S100B, Glypican-1, and non-coding RNA to name a few, were shown to stratify patients participating in various clinical trials into responders versus non-responders, healthy controls and disease-free patients versus cancer patients, and/or cancer patients with differing survival outcomes (104, 107, 129–133). The gene discussed is CD63; the disease is cancer.