In the last 30 years the incidence and prevalence of gastroenteropancreatic neuroendocrine tumors (GEP-NETs) has increased substantially. This could be partly due to improvements in diagnostic imaging, which lead to the incidental diagnosis of asymptomatic cases. However, despite these improvements, patients typically experience long delays before they are diagnosed. In this review, we discuss both the limitations and advances in our understanding of the pathogenesis, molecular and cellular biology, diagnosis, classification, staging, and treatment of GEP-NETs in order to identify which factors could be contributing to the delay in diagnosis and timely treatment of these patients. Within this context, the results from the most relevant clinical trials the available targeted therapies for the treatment of GEP-NETs, such as the "RAD001 in Advanced Neuroendocrine Tumors," will be discussed.