GAST and duodenal neuroendocrine tumor, well differentiated, low or intermediate grade: In contrast, no proliferative gastrin cell lesions were identified in patients with sporadic non-MEN1-based gastrinomas.116 Unlike the duodenal neuroendocrine tumors, hyperplastic G-cells did not exhibit LOH of the MEN1 locus, thus implicating them as potential precursor lesions to DGASTs.116 However, the genetic and environmental stimuli that induce the transition of hyperplastic gastrin cells into tumors remains to be elucidated.