This single-center, retrospective cohort study included patients with ERBB2+ MBC and CNS disease, including parenchymal brain metastasis, leptomeningeal disease (LMD), or dural metastasis, who were treated between August 2010 and April 2022 at Memorial Sloan Kettering Cancer Center. The gene discussed is ERBB2; the disease is Langer mesomelic dysplasia.