Gastroenteropancreatic neuroendocrine tumors (GEP-NETs) are rare, heterogeneous tumors arising from neuroendocrine cells throughout the body. They were previously called gastrointestinal carcinoids and islet cell tumors. Functional tumors produce hormones and cause symptoms like diarrhea, flushing, or hypoglycemia, while non-functional tumors are asymptomatic until they cause mass effects. The 2010 WHO classification divides them into well-differentiated NETs (G1–G3) and poorly differentiated NECs, based on mitotic count and Ki67 staining. Incidence data are limited but rising, possibly due to better understanding and imaging. The annual incidence is 1.3–3.5/100,000, with the small intestine being the most common site (35% of cases), followed by the appendix. Pancreatic NETs have an incidence of 0.1–0.3/100,000. Prognosis depends on metastasis and grading. Complete resection is the only cure, and debulking may help if >90% of the tumor is removed. Surgery may also relieve symptoms in stage IV patients. Diagnosis involves imaging like CT or MRI to detect metastases. PET/CT with somatostatin receptor-targeting agents (e.g., 68Ga-DOTA-TATE) is highly sensitive for functional tumors, aiding in therapy. In contrast, 18F-FDG PET/CT is preferred for NECs. Somatostatin receptor radionuclide therapy is not feasible in NECs. Due to their complexity, treatment requires a multidisciplinary approach.Gastroenteropancreatic neuroendocrine tumors (GEP-NETs) are rare, heterogeneous tumors arising from neuroendocrine cells throughout the body. They were previously called gastrointestinal carcinoids and islet cell tumors. Functional tumors produce hormones and cause symptoms like diarrhea, flushing, or hypoglycemia, while non-functional tumors are asymptomatic until they cause mass effects. The 2010 WHO classification divides them into well-differentiated NETs (G1–G3) and poorly differentiated NECs, based on mitotic count and Ki67 staining. Incidence data are limited but rising, possibly due to better understanding and imaging. The annual incidence is 1.3–3.5/100,000, with the small intestine being the most common site (35% of cases), followed by the appendix. Pancreatic NETs have an incidence of 0.1–0.3/100,000. Prognosis depends on metastasis and grading. Complete resection is the only cure, and debulking may help if >90% of the tumor is removed. Surgery may also relieve symptoms in stage IV patients. Diagnosis involves imaging like CT or MRI to detect metastases. PET/CT with somatostatin receptor-targeting agents (e.g., 68Ga-DOTA-TATE) is highly sensitive for functional tumors, aiding in therapy. In contrast, 18F-FDG PET/CT is preferred for NECs. Somatostatin receptor radionuclide therapy is not feasible in NECs. Due to their complexity, treatment requires a multidisciplinary approach.