The median percentage of HER2-positive tumor cells was 41.1 % (range 2.0–74.2 %), 34.0 % (range 0.0–90.7 %), 30.8 % (range 0.0–99.7 %), and 13.5 % (range 0.0–98.0 %) per case, layer, region, and biopsy specimen, respectively. This evidence concerns the gene ERBB2 and neoplasm.