The two BC types are primarily distinguished on the basis of their selective expression of either the neuropeptide cholecystokinin (CCK) or the calcium-binding protein parvalbumin (PV) (Nunzi et al. 1985; Kosaka et al. 1987; Freund and Katona 2007; Lee and Soltesz 2011; Booker et al. 2013, 2017). This evidence concerns the gene CCK and breast cancer.