The randomized phase III EMILIA trial established T-DM1 as the standard second-line treatment for patients with HER2-positive aBC previously treated with trastuzumab and a taxane, showing superiority over lapatinib + capecitabine (XL) in terms of PFS and OS (mOS of 29.9 months (95% CI 26.3–34.1) vs. 25.9 (95% CI 22.7–28.3); HR 0.75 (95% CI 0.64–0.88) [71]. Here, ERBB2 is linked to aneurysmal bone cyst.