Histological staining of actin, alpha2, smooth muscle (SMA), a marker of activated fibroblast upregulated by persistent oxidative stress (Martinez‐Outschoorn et al, 2010; Toullec et al, 2010; Balliet et al, 2011; Artaud‐Macari et al, 2013) accumulated in CAF from HER2 and TN tumours compared to LumA tumours (Fig 4D and E) and was negatively correlated with H2AX protein levels (Fig 4F). Here, ERBB2 is linked to neoplasm.