CASR and gastrin-producing neuroendocrine tumor: Quantification demonstrated that CASR mRNA expression was significantly higher in normal islets (mean relative expression = 1, range = 0.46–1.30) when compared to gastrinomas, insulinomas, and NF‐PNETs (mean relative expression = 0 and p < .0001 for all tumour subtypes, Figure 1B).