CD81 and neoplasm: Conversely, the remaining 13 markers (CD105, CD133/1, CD14, CD142, CD146, CD29, CD44, CD56, HLA-DR/DP/DQ, MCSP, and the three tetraspanins CD9, CD63, and CD81 specially enriched in the membrane of EVs and often used as exosome biomarkers) showed higher MFIs than their respective isotypic controls, indicating their presence on the surface of the tumor-derived EVs (Figure 2B,C).