CCKBR and medullary thyroid gland carcinoma: The overexpression of cholecystokinin receptor subtype 2 (CCK2R) is involved in various malignancies, such as medullary thyroid carcinoma (MTC), small cell lung cancer (SCLC), and neuroendocrine tumours (NET) [3, 4] and therefore represents an interesting target for peptide receptor radionuclide imaging and therapy.