ERBB2 and gastric cancer: However, the same HER2 guidelines are vague regarding the number of biopsy specimens, the tumor content per biopsy specimen, or the location from which the biopsy specimen should be obtained within the tumor, and simply recommend that “an adequate number of viable biopsy specimens (ideally six to eight) are required.” The current guidelines do not provide any evidence for the recommendations made and do not seem to consider the suggested relationship between HER2 positivity and histological subtype, grade of differentiation [7–11], and tumor location [12] in GC.