The increased EpOMEs were deduced to be mainly due to the upregulation of CYP2J2 based on the IHC analysis of the protein expression of CYP2J2/2C8/2C9/2C18/2C19 in the tumor tissues from the patients with four subtypes of BC and controls, and the mRNA and protein levels of CYP2J2/2C8/2C9/2C18/2C19 in multiple TNBC cells, other BC cells, and normative mammary cells, which was also supported by the increased Cyp2j8 in MMTV-PyMT mice. Here, CYP2J2 is linked to breast cancer.