Well-differentiated Neuroendocrine Tumors

Comments:
Introduction: The 2019 WHO Classification subdivides neuroendocrine neoplasms (NENs) of gallbladder and bile ducts into three types: 1) well-differentiated neuroendocrine tumors (WDNETs; previously called carcinoids); 2) poorly-differentiated neuroendocrine carcinomas (NECs; small cell or large cell phenotype); and 3) mixed neuroendocrine-nonneuroendocrine neoplasms - where each component makes up at least 30% of the tumor. Conventional gallbladder adenocarcinomas with scattered neuroendocrine cells are not included in this classification.

NENs involve gallbladder more often than bile ducts and NECs are more common than WDNETs. Any portion of gallbladder may be affected. In extrahepatic biliary tract, the distal common bile duct is the usual site. This image shows an example of WDNET of gallbladder. A Rokitansky-Aschoff sinus is partially visible at the top.