CCKBR and medullary thyroid gland carcinoma: Cholecystokinin-2 receptors (CCK2R) are overexpressed in various cancers, including the majority of medullary thyroid carcinomas (MTC), more than half of small cell lung cancers (SCLC), and various neuroendocrine tumors (NETs).8,9 This expression pattern makes CCK2R an attractive target for nuclear medicine imaging and therapy.