Immunohistochemical staining for HRGβ1 in primary breast cancer specimens. (a) Examples of high and low HRGβ1 expression. Scale bars = 20 μm. (b) Box-plots illustrating cytoplasmic HRGβ1 immunohistochemistry assessed by H-score analysis in membrane (mem) epidermal growth factor receptor (EGFR)-negative, erbB2-negative and erbB3-negative primary breast cancer versus membrane EGFR-positive, erbB2-positive and erbB3-positive primary breast cancer. A significant positive correlation between cytoplasmic HRGβ1 expression and membrane erbB receptor positivity was only seen with EGFR (Mann–Whitney U test, P = 0.04). (c) Box-plots illustrating cytoplasmic HRGβ1 immunohistochemistry assessed by H-score analysis in membrane (mem) phosphorylated erbB2-negative versus membrane phosphorylated erbB2-positive primary breast cancer and in nuclear (nuc) phosphorylated ERK1/2-negative versus nuclear phosphorylated ERK1/2-positive primary breast cancer (Mann–Whitney U test, P = 0.006 and P = 0.017, respectively), and scatter plot illustrating the significant positive correlation between expression levels of nuclear phosphorylated AKT and cytoplasmic HRGβ1 in the same samples (Spearman rank test, P = 0.044).