The percentage of HER2-positive tumor cells was significantly higher in the luminal layer than in the deeper layer [median percentage of HER2-positive tumor cells in the luminal layer of 60.3 % (range 3.9–90.7 %) vs 21.7 % (range 0.0–67.2 %) for the deeper layer; p < 0.001]. Here, ERBB2 is linked to neoplasm.