ESR1 and breast cancer: There was a statistically significant difference in breast cancer-specific survival between tumours with high vs. low expression of MMP-1 in tumour cells (cut-off value 70%, p = 0.0171) (Figure 4), tumour grade I vs. III (p = 0.0099), triple-negative vs. non-triple-negative breast cancers (p = 0.0137), basal-like vs. non-basal-like breast cancers (p = 0.0103), low vs. high bcl-2 expression (cut-off value 25%, p = 0.0003) and high vs. low estrogen receptor expression (cut-off value 10%, p = 0.0013).