ERBB2 and neoplasm: To investigate the causes of elevated plasma EpOMEs, we first examined the protein expression of their synthetic enzymes CYP2J2 and CYP2Cs in the tumor tissues of the patients with different subtypes of BCs, including HER2+, Luminal A, and Luminal B, as well as TNBC, and normative breast tissues from the non-tumor (Control) patients using immunohistochemical (IHC) staining.