Surgery for Neuroendocrine Tumors of the Stomach, Small Intestine, Large Intestine, and Rectum: Techniques and Potential Complications

Gastrointestinal neuroendocrine tumors (GI-NET) are rare, histologically distinct neoplasms, with unique site-specific traits, and often indolent biological behavior (Ahmed et al., World J Gastrointest Oncol 12:791–807, 2020). The site of origin dictates the behavior of the tumor and thus, each type of GI-NET is approached differently from a surgical and medical perspective. Gastric NETs (~7% of GI-NETs) arise from enterochromaffin-like cells (ECL) and are classified into three types (Ahmed et al., World J Gastrointest Oncol 12:791–807, 2020, Sato et al., World J Gastroenterol 22:6817–28, 2016). Types 1 and 2 are gastrin dependent, while Type 3 is gastrin independent. Neuroendocrine tumors of the small intestine (SI-NETs) are the most common malignancy of the small bowel and make up 45% of all GI-NETs. Many patients with SI-NETs have metastatic disease at diagnosis and up to 60% present with carcinoid syndrome. Appendiceal NETs (~16% of GI-NETs) are often diagnosed incidentally following appendectomy for appendicitis. Additional surgery for these tumors is based on the risk assessment of residual or future metastatic disease. Rectal NETs (20–40% of GI-NET) are increasing in prevalence as screening colonoscopy becomes more accessible in North America (Dasari et al., JAMA Oncol 3(10):1335–42, 2017, Lee et al., Clin Gastroenterol Hepatol 17(11):2212–7 e1, 2019). The majority of rectal NETs are removed with biopsy and often do not require additional management. Surgery for this diverse group of GI-NETs is dependent on the presenting stage, the site of origin, and the presence or absence of a functional endocrinopathy.