ERBB2 and medulloblastoma: We extended our Western blotting analyses to serum exosomes from patients with medulloblastomas compared to those from healthy donor sera (Figure 3 A), showing reactivity with patient serum exosomes against ERBB2, and GPNMB (both brain tumor antigens), but general reactivity against canonical exosome markers HSP/HSC70, CD63, and CD9.