For IHC 3+ samples, 3.1 % (biopsies only), 26.8 %, 31.0 %, and 39.0 % of cases showed HER2 reactivity in <10 %, 10 to 30 %, 31 to 79 %, and 80 to 100 % of tumor cells, respectively. The gene discussed is ERBB2; the disease is neoplasm.