HER2 negative tumors had a lower probability of having R1 status than the HER2 positive tumors, with an OR of 0.5000 (95% CI 0.251–0.996, p = 0.049). Table 4 summarizes results from univariable and multivariable binary logistic regression analyses concerning the risk of R1 status with cavity shaving versus standard procedure in the total cohort, in histologic subgroups, and in the subgroup of patients with invasive ductal carcinoma. This evidence concerns the gene ERBB2 and invasive ductal breast carcinoma.