CD9 and posterior cortical atrophy: Importantly, as previous work has demonstrated that particles in a plasma can non-specifically associate or aggregate with platelet and EV membranes, to ensure that our identified STEAP1-positive EVs were not associated with platelets and platelet-derived EVs we analyzed 10 healthy and 10 PCa plasma samples for platelet specific markers CD9, CD41, and CD42a (Supp.