ERBB2 and ductal breast carcinoma in situ: The associations were mostly unchanged after we performed imputation for those variables (exposures and potential confounders) that had missing rates of less than 20% (Table 2), although the associations for nuclear grade, punctate necrosis, and HER2 positivity were closer to the null, while there was a slight (statistically non-significant) increase in risk of IBC for those who were ER negative (Table 3).There was a strong positive association between involved DCIS margins and risk of ipsilateral IBC, albeit with very wide confidence intervals (OR = 6.02, 95% CI 1.25–29.12) (Table 4).