To characterize the association between DCIS and IBC, we applied multivariable models of IBC as a function of a six-level categorical variable describing chromosomal gains at regions 1q, 8q24 and 11q13, along with age at diagnosis, race, hormone receptor status, histological grade and the presence of HER2 gain (Table 4 and see Additional file 4). The gene discussed is ERBB2; the disease is ductal breast carcinoma in situ.