OBJECTIVETo explore the primary site and pathological feature of neuroendocrine neoplasm (NEN), especially the NEN of digestive system.

METHODSClinicopathological data of NEN patients at China-Japan Friendship Hospital from January 2012 to December 2016 were retrospectively analyzed. Tumor primary sites were summarized. Association between tumor site and pathological grading in gastroenteropancreatic neuroendocrine neoplasm(GEP-NEN) was examined.

RESULTSThere were a total of 903 cases of NEN. Sites of primary tumor included the digestive system in 699 cases(77.4%), the thorax(including lung, thymus and mediastinum) in 87 cases(9.6%), other sites in 60 cases (6.6%), unknown in 57 cases(6.3%). Among 699 GEP-NEN cases, the primary sites included the stomachin in 207 cases (29.6%), pancreas in 201 (28.8%), rectumin in 185 (26.5%), duodenum in 43(6.2%), jejunum and ileum in 18(2.6%), appendix in 15 (2.1%), gallbladder in 11(1.6%), esophagus in 10(1.4%), and the colon in 9 cases (1.3%). Pathologically, the tumor grading was neuroendocrine tumor (NET) G1 in 336 cases(48.1%), NET G2 in 203 cases (29.0%), neuroendocrine carcinoma (NEC) G3 in 139 cases (19.9%). All the esophagus NEN(10/10), most gallbladder NEN(9/11) and colon NEN(6/9) were poorly-differentiated NEC (G3), while all appendix NEN(15/15), most stomach NEN(147/207, 71.0%), pancreas NEN (156/201, 77.6%), rectum NEN (169/185, 91.4%), duodenum NEN (31/43, 72.1%), jejunum and ileum NEN(16/18, 88.9%) were well-differentiated NET G1 or G2.

CONCLUSIONSThe most common primary site of NEN is the digestive system. The stomach, pancreas and rectum are most common primary sitesof GEP-NEN. Difference in pathological grading is quite greatin different primary sites of GEP-NEN. Most NENs fromesophagus, colon and gallbladder are poorly-differentiated NEC.