Neuroendocrine tumors and smoking

Funding: None. Conflict of interest statement: The authors declare that they have no conflict of interest. Data Availability Statement: All relevant data are within the paper. Abstract Neuroendocrine cells are dispersed around the body and can be found within the gastrointestinal system, lungs, larynx, thymus, thyroid, adrenal, gonads, skin and other tissues. These cells form the so-called ‘’diffuse neuroendocrine system’’ and tumors arising from them are defined as neuroendocrine tumors (NETs). The traditional classification of NETs based on their embryonic origin includes foregut tumors (lung, thymus, stomach, pancreas and duodenum), midgut tumors (beyond the ligament of Treitz of the duodenum to the proximal transverse colon) and hindgut tumors (distal colon and rectum). NETs at each site are biologically and clinically distinct from their counterparts at other sites. Symptoms in patients with early disease are often insidious in onset, leading to a delay in diagnosis. The majority of these tumors are thus diagnosed at a stage at which the only curative treatment, radical surgical intervention, is no longer an option. Due to the increasing incidence and mortality, many studies have been conducted in order to identify risk factors for the development of NETs. Still, little is known especially when it comes to preventable risk factors such as smoking. This review will focus on smoking and its contribution to the development of different subtypes of NETs.