MC1R and colorectal neoplasm: Radiopharmaceuticals have been successfully developed for imaging of somatostatin receptors (neuroendocrine, gastroenteropancreatic, breast, brain, and small cell lung cancer tumors), prostate-specific membrane antigen (prostate cancer), gastrin-releasing peptide receptor (prostate, breast, pancreas, small cell lung cancer, and colorectal tumors), melanocortin 1 receptor (melanomas), and integrin ανβ3 receptor (brain, lung, ovary, breast, and skin cancer), to name a few [504].