CD9 and breast cancer: In a clinical study, the ddiPCR approach simultaneouslyprofiled EV proteins associated with breast cancer and hepatocellularcarcinoma, showing significant differences in multisubpopulation EVcounts between cancer patients and healthy controls that were basedon specific EV surface markers for each cancer type. Notably, ddiPCR successfully profiled biomarkers such asCD9/CD63/CD81, HER2, and EpCAM for breast cancer and CD9/CD63/CD81,GPC-3, and EpCAM for hepatocellular carcinoma.