ERBB2 and breast neoplasm: Presence of HER2 amplification in CISH in the breast tumor and tumor HER2 expression in immunohistochemistry were closely associated; 141 (95.2%) of the 148 breast tumors that did not contain HER2 amplification did not express HER2, whereas 57 (80.3%) of the 71 tumors with HER2 amplification expressed HER2 protein (P < 0.0001).