To confirm this, we screened another set of 33 specimens of Luminal A-like invasive cancer (n = 28) or its putative precursor lesion (ER(+)HER2(−) DCIS) (n = 5) for der(1;16) using FISH and identified an additional eight der(1;16)(+) specimens, two from premenopausal and six from postmenopausal patients (Fig. 3a and Extended Data Figs. 7 and 8). Here, ERBB2 is linked to ductal breast carcinoma in situ.