For SBS13-like, mean relative contribution was significantly higher in those aged 30–34 (p = 0.026) and 35–39 (p = 0.015) relative to <30 years, higher in the HER2-enriched subtype relative to luminal (p = 0.034), and T3 tumours relative to T1 (p = 0.011). This evidence concerns the gene ERBB2 and neoplasm.