In subsequent studies, ISL1 has been shown to also be expressed in pancreatic, duodenal, rectal and colonic NETs, in addition to Merkel cell carcinoma, pheochromocytoma/paraganglioma and medullary thyroid carcinoma (Table 1 and Figure 1) [14,15,16,17]. The gene discussed is ISL1; the disease is hereditary pheochromocytoma-paraganglioma.