Cannabinoid receptors have been documented to be present in breast tissue; CB1 immunoreactivity was expressed in 28% of human breast cancer samples [127] and immunohistochemistry studies have revealed the presence of CB1 in 14% of human breast cancer tissues expressing ErbB2, which is a member of the epidermal growth factor (EGF), but interestingly with no relationship between CB1 and ErbB2 expression [128]. This evidence concerns the gene CNR1 and breast cancer.