ERBB2 and breast cancer: FMO2 was downregulated in HER2+ breast cancer (P < 0.0001) (Figure 2E and Supplementary Table 1), mucinous histological type (P < 0.0001) (Figure 2F and Supplementary Table 1), and pathological tumor stage II (P = 0.0067) (Figure 2G and Supplementary Table 1).