Reports in the literature show widely varying percentages of cancers expressing CCK2R (see Table 1 for summary), with gastric adenocarcinomas [23], medullary thyroid carcinoma [4, 20], colorectal carcinoma [7, 8], small cell lung carcinoma [6], and pancreatic carcinoma [16] overexpressing the receptor when compared to matched normal tissues. This evidence concerns the gene CCKBR and cancer.