AHR and neoplasm: Although APOBEC mutagenesis was equally distributed in luminal and non-luminal BCa tumours (Additional file 3: Fig. S13), the AHR Q383H mutation (n = 8) occurred only in luminal BCa tumours and overall AHR genomic alterations (mutations and amplifications) and ARNT amplifications were enriched in this subtype (Fig. 6d).