ERBB2 and breast cancer: This loss of junctional integrity resulted in increased MVN permeability in the vicinity of the SKBR3 and MDA‐MB‐468 tumoroids, as measured by the diffusion of dextran (a large model molecule of 70 kDa often used to benchmark vascular permeability[30]), as well as therapeutic monoclonal antibodies (mABs) trastuzumab (HER2/ERBB2‐targeting)[31] and cetuximab (EGFR‐targeting),[32] which are used in the treatment of breast cancer (Figure 2b).