ERBB2 and neoplasm: Several studies revealed a better [2,3,4,5,6,7,8,9,10] or worse [11,12] prognosis for patients with HER2-low tumor when compared to those with HER2-zero (defined as IHC 0) tumor in various settings, while others hardly found any difference between HER2-low and HER2-zero tumors [13,14,15,16,17,18,19,20].