ERBB2 and breast cancer: When comparing the two BC groups, there was a significant increase in Bacteroides (q < 0.01), Blautia (q < 0.05), Lachnospira (q < 0.05), Lawsonia (q < 0.01), and Oscillospira (q < 0.01) in the HR+HER2- group compared to the HR+HER2+ group (Figure 4).