In comparison to normal breast tissues, authors reported higher GJB2 gene expression in invasive ductal carcinoma of the breast and very intense GJB2 gene expression in most estrogen receptor (ER) negative breast cancer tissues; on the contrary, most ER-positive breast cancer samples exhibited weak staining that was not statistically significant in comparison to normal tissue. This evidence concerns the gene GJB2 and invasive ductal breast carcinoma.