ERBB2 and breast cancer: As for the low ΔR2* measurements in luminal A breast cancer, this can be explained by the fact that the magnitude of BOLD signal decrease following a hyperoxic gas challenge depends on the vascular maturity in the tissue, i.e., the ability of vessels to transport oxygen-enriched blood [32,33], and clinical studies using contrast-enhanced MRI have shown that luminal A tumors develop the most functional blood vessels in comparison to Her2+ and triple-negative tumors [34].