We reported dramatic elevated levels of AhR proteins in human breast carcinoma (HBC) cell lines from advanced malignancy (MDA-MB231, MDA-MB468, MDA-MB435s, MT2, NT, MCF7 breast cancer cell lines), while less levels were expressed in HBC derived from early stages of malignancy (T47D, MDA-MB-436 cell lines) and in immortalized and primary human mammary epithelial cells. This evidence concerns the gene AHR and breast cancer.