ERBB2 and breast carcinoma: Interestingly, breast cancer subtypes are associated with the diverging tropism of metastatic spread in humans, as, for example, hormone receptor (HR)-positive breast cancer preferably metastasizes to the bone, whereas human epidermal growth factor 2 (HER2)-positive or triple-negative (HR-/HER2-) breast cancers more probably spread to visceral organs [2,8].