NPY and neoplasm: hY1R-preferring agonists, especially [F7, P34]-NPY, have shown great potency in imaging tumor sites in patients with breast cancer, thanks to the high frequency and density of Y1 receptors on breast tumor cells, as well as the discrepancy of the receptor subtypes between breast carcinomas (Y1 receptors) and non-neoplastic breast (Y2 receptors) [225,226].