Although PRL could induce estrogen receptor-positive breast cancer (BC) in a murine model (Campbell et al., 2019), and initiate the transformation of normal ductal epithelial cells (Grible et al., 2021), many epidemiological studies have not shown an increased risk of BC in the population with hyperprolactinaemia (Dekkers et al., 2010; Berinder et al., 2011; Dekkers et al., 2015). This evidence concerns the gene PRL and breast cancer.