With regard to the gut microbiota, fecal samples from women with HER2+ BCs are characterized by lower α-diversity and lower levels of certain genera of Firmicutes (i.e., Clostridium, Blautia, Coprococcus, Ruminococcus, SMB53 genus), whereas they have more Bacteroidetes compared with HER2- patients (70), suggesting that specific gut microbial compositions may represent a risk factor for this tumor subtype. Here, ERBB2 is linked to neoplasm.