Classifying tumor samples by subtypes, i.e. “luminal”, “HER2-positive” and “triple-negative breast cancer (TNBC)” [22], based on immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) data for estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2), revealed an increase in NMU mRNA expression in HER2-positive and triple-negative breast carcinomas (median FC: 3.0 and 3.5) (Figure 1B). Here, ERBB2 is linked to triple-negative breast carcinoma.