Rare Functioning Pancreatic Endocrine Tumors - O’Toole, D; Salazar, R; Falconi, M; Kaltsas, G; Couvelard, A; de Herder, W W; Hyrdel, R; Nikou, G; Krenning, E; Vullierme, M P; Caplin, M; Jensen, R; Eriksson, BFrascati Consensus Conference; European Neuroendocrine Tumor Society (Neuroendocrinology, 2006)