Patients with ERBB2-positive breast cancer and CNS-only metastasis are at a high risk for CNS-related death but have longer overall survival than those with concomitant extracranial metastases.

Each ERBB receptor has distinct locations and numbers of tyrosine phosphorylation sites on its C-terminal tails; there are twelve on ERBB1, six on ERBB2, and eleven on ERBB3 (Jones et al.