ISL1 and pancreatic insulinoma: Among 24 islet 1-positive PanNETs [22] investigated (11 G1 and 13 G2 tumors; Table 1, Supplementary Figure 2), scattered cytoplasmatic RSUME immunopositivity was observed in insulinomas (n = 7; Figure 1C, 1E) whereas RSUME was absent in the vast majority of the other PanNETs including 4 somatostatin expressing tumors (Figure 1B, 1D, 1E; Supplementary Figure 1).