<p>Neuroendocrine neoplasms [NENs] are a group of rare tumors that evolve from neuroendocrine cells and show different morphological patterns and clinical and biological characteristics. These tumors are diverse in terms of sites of origin, functional status, degree of aggressiveness, and patients outcome. Although they share certain histopathological features regardless of their sites, they have been studied in an organ–specific manner and their grading remain site specific. In this review, we provide on the contemporary understanding of neuroendocrine tumors, pathological and immunohistochemical characteristics that help in tumor diagnosis paving the way for the development of new diagnostic techniques. Additionally molecular alterations, genetic mut ations and the biomarkers used to detect tumors at an earlier stage were summarized. Many researches evaluating prognostic markers and allowing for personalized treatment options are recommended.</p>