Prior to quantification of exosomal miRNAs, the extractions of exosomes from a healthy woman and a patient with DCIS, lymph node-negative BC, lymph node-positive BC and recurrent BC were verified on a Western Blot using antibodies specific for the exosomal marker CD63 and the miRNA binding protein AGO2. Here, AGO2 is linked to ductal breast carcinoma in situ.