SYP and neoplasm: For a metastatic gastrointestinal NET, grade 1 or 2 stable at inclusion NET diagnosis criteria: Confirmed either by biopsy of the primary tumor or liver metastasis And by immunohistochemical expression of both chromogranin A and synaptophysin Assessment of tumor differentiation according to the WHO 2010 classification and its proliferation rate was evaluated by estimates of Ki67 Tumors with Ki67 ≤ 2% = grade 1 Tumors with Ki67 3–20% = grade 2