Evaluating a large number of non-breast tumors for HER2 protein expression, including tumors without ERBB2 amplification, is necessary to examine the potential clinical use of NGS-based ERBB2 amplification status relative to the HER2 IHC score, as well as to determine whether a high estimated CN value threshold should be considered for non-breast cancers. The gene discussed is ERBB2; the disease is breast cancer.