MEN1 and gastrin-producing neuroendocrine tumor: It is described in the ICS from the EU, “At least 70–80% of MEN1 gastrinomas have been demonstrated to be malignant at the time of diagnosis and to show lymph node and/or liver metastasis, although the primary D-NEN(s) may be microgastrinomas as small as 1–2 mm in size (LE: 2b)” [6 articles are cited] [8].