CCKBR and medullary thyroid gland carcinoma: The cholecystokinin subtype 2 receptor (CCK2R) represents a clinically relevant biomolecular target for nuclear medicine applications owing to its overexpression in a variety of human tumors, such as medullary thyroid carcinoma (MTC), small cell lung cancer (SCLC), astrocytomas, stromal ovarian cancers or gastrointestinal stromal tumors (GIST) [1,2,3,4,5,6].