Gastric neuroendocrine tumors: A review of pathology and updated roadmap to surgical management

Abstract

Neuroendocrine tumors are a rare cancer, with those arising in gastric tissue even less commonly. With increasing recognition through endoscopy, these tumors are diagnosed in more patients each year. As a rare and growing entity, our understanding of these tumors, the way we characterize them, and treatment are changing rapidly. Thus, we sought to provide an updated review of pathology and management, highlighting the latest guidelines and evidence for surgical treatment. Much of the general treatment paradigm is from consensus guidelines put forth by the European Neuroendocrine Tumor Society and the North American Neuroendocrine Tumor Society; however, future research is needed to help guide further surgical decision-making around intermediate grade and intermediate size type III tumors, as well as systemic therapies in the perioperative and nonoperative settings for high-grade tumors.

Key Words: Gastric; Carcinoid; Neuroendocrine tumor; Stomach; Endoscopic; Surgical management

Core Tip: Gastric neuroendocrine tumors are a rare pathology, with rising incidence as endoscopic diagnoses increase. Management, including surgical decision-making, is guided by subtype as well as tumor size and grade, which have been shown to be prognostic. There still exist areas that lack consensus, namely for extent of surgery for intermediate-grade and medium-sized type III tumors, as well as in clarifying the role of systemic therapies for high-grade tumors in the perioperative settings and for nonoperative metastatic disease specifically for gastric-originating tumors. Existing practice guidelines provide surgeons the framework for treatment, however future work is needed to fill gaps in decision-making consensus.

INTRODUCTION

Neuroendocrine neoplasms (NENs) are a rare type of cancer but are growing in incidence[1]. They arise from cell types with hormonal properties, which are often responsible for their disease manifestations. NENs range from well-differentiated neuroendocrine tumors (NETs) to poorly differentiated neuroendocrine carcinomas (NECs)[2,3]. NET malignancy potential ranges in severity, while NECs are characteristically aggressive and malignant. Many medical professionals tend to use the term carcinoid interchangeably with any neuroendocrine neoplasm, however over time it has developed a more specific definition. “Carcinoid” is a term first coined in 1907 and was used to describe these often slow-growing gastrointestinal tumors with polymorphic cytoplasm and prominent nuclei[4,5]. Now, it is used to specifically describe well-differentiated non-pancreatic gastrointestinal NETs[6,7]. These neuroendocrine tumors arise in various locations, including the stomach.

Gastric NETs (G-NETs) are a particularly rare subtype of neuroendocrine tumor but have nonetheless been rising in prevalence over the last 3 decades[1,8,9]. It is understood that most G-NETs arise from gastric enterochromaffin-like (ECL) cells. Management varies based on the location, size, histologic features, and other tumor characteristics. Gastric NETs are classified based on the World Health Organization (WHO) pathophysiological system: Type I (most common), type II (least common), and type III[10-14]. Type I and II tumors often arise in the context of hypergastrinemia, with type I related to atrophic gastritis vs type II related to syndromes such as Zollinger-Elison syndrome. They are often multifocal and less aggressive than type III. In contrast, type III tumors often arise without the context of hypergastrinemia and are often higher grade. Type III gastric NETs clinically present as an aggressive singular tumor rather than from the neuro-hormonal manifestations (Table 1).

Table 1 Characteristics of gastric neuroendocrine tumors subtypes.

	Type I (75%-80%)	Type II (5%)	Type III (15%-25%)
Gastrin levels	High gastrin	High gastrin	Normal gastrin
Gastric acid	pH > 4, hypo- or achlorhydria	pH < 2, hyperchlorhydria	pH < 4, normal gastric HCL
Surrounding gastric mucosa	Atrophic gastritis	Corpus mucosal hypertrophy	Normal mucosa
Underlying cause	Autoimmune atrophic gastritis	Gastrinoma related to Zollinger-Ellison, MEN-1 syndrome	Sporadic mutations
Tumor number	Multifocal	Multifocal	Singular
Tumor size	Smaller, < 2 cm	Smaller, < 2 cm	Larger, > 2 cm
WHO grade	1-2	1-2	1-3
Ki-67%	Lower	Lower	Higher
Malignancy potential	Low	Low	High

This table compares qualities between type I, II, and III G-NETs, as their characteristic behavior, presentation, and management differ. MEN-1: Multiple endocrine neoplasia type 1; WHO: World Health Organization.

In this review, we seek to provide an overview of disease epidemiology and pathology to provide context before focusing on treatment clinical decision-making. We will delve deep into surgical management, providing a roadmap for treating this rising population of patients, highlighting gaps in consensus.

EPIDEMIOLOGY

While uncommon and making up an estimated 0.3%-1.8% of all gastric malignancies, G-NET rates have been rising globally[1,8,15-17]. According to the American National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) database, the incidence of gastric carcinoids is 1.4 per 100000 people[9]. The rate of gastric NETs has increased 15-fold from 1973 to 2012[1]. Among all neuroendocrine tumors, the percentage of which were gastric from 1950–1969 was 2.3%, which increased to 6.0% from 2000-2007[14]. Similarly, in England from 1971 to 2006 there has been a relative increase in gastric NETs, of 2325% in men and 4746% in women[15].

This rising incidence is likely in-part due to increased diagnosis facilitated by widespread endoscopy use and advances in immunohistochemistry[18-20]. Tumors are more readily diagnosed, monitored more closely, and can be endoscopically biopsied or therapeutically resected. Given the increasing rates have overlapped with the more widespread use of acid-suppressing agents like proton pump inhibitors (PPI), some studies question PPI use as a potential cause of ECL cell proliferation. It is also possible that this is a coincidental association given the routine diagnostic endoscopy-use to investigate gastric pathology in patients treated with PPIs[8]. There is presently not sufficient evidence to suggest a causal relationship with long-term proton pump inhibitor use[21].

Carcinoid tumors are most common in women, with an age-standardized incidence rate reported to be 0.5 per 100000 noted in a SEER analysis of 13279 cases from 2000-2019 in the United States. Men have a reported incidence of 0.37 per 100000. In looking at race and ethnicity, Hispanic patients were found to have the highest incidence in this SEER analysis, with Hispanic women having an incidence of 0.91 per 100000 and men having an incidence of 0.49 per 100000. They noted two-times the number of cases in patients 55 years-old and greater vs those less than 55[22]. A subsequent SEER analysis of a sample of 28199 people showed that gastric carcinoids were most common in people ages 50 and older; of people with carcinoid diagnosed 2016-2018, 81.0% were greater than or equal to 50 years of age, and 19.0% were 20-49, with similar rates of diagnoses from 2000 to 2002[23]. This is supported by other studies with similar age trends[8,22-24].

There are also epidemiologic patterns noted based on the subtype of gastric cancer. The most common subtype is type I (75%-80% of NENs), followed by type III (15%-25%), and the least common type II (5%). Aligning with the associated pathologies, type I gastric carcinoid tumors, which are associated with atrophic gastritis, are more commonly found in women, rather than men, and in people of white race[12,25,26]. For type II, there has been no specific noted association by sex[27], however given its association with gastrinomas and Zollinger-Ellison syndrome, it has been noted to affect younger patients relative to the other 2 types[28]. For type III tumors, a systematic review of 31 articles showed a median age of 58 years and slight predominance of disease in men (59.3% of the population)[29].

PATHOPHYSIOLOGY AND RISK FACTORS

The pathogenesis of gastric NETs overall can be divided into 2 categories: Gastrin-dependent and gastrin-independent. The understanding of normal gastric physiology is vital to understanding the deviance which results in type I and II gastrin-dependent G-NETs[3,30]. Parietal cells in the stomach are responsible for secreting gastric acid upon stimulation by the vagus nerve (via acetylcholine, ACh), histamine (via ECL cell paracrine mechanism), and gastrin (endocrine mechanism) among other stimuli. ECL cells reside in the fundus of the stomach within gastric glands. ECL cells respond to the hormone gastrin which is released by G cells in the antrum of the stomach. Gastrin is normally secreted by G cells in the gastric antrum, which then bind to the gastrin receptors on ECL cells to signal the ECL-mediated release of histamine, which then serves as a potent parietal cell activator via the H2 receptor[30]. Moreover, D cells secrete somatostatin which act via paracrine mechanism to directly inhibit parietal cell activity and indirectly by inhibiting ECL cells (Figure 1). It is the dysregulation of this process via increased gastrin levels which is implicated in the pathogenesis of type I and type II NETs.

Figure 1 Gastric physiology, interactions between enterochromaffin-like and parietal cell. This is a simplified schematic of interactions between enterochromaffin-like (ECL) and parietal cells that result in the normal physiologic release of gastric acid. This is an original figure. Ach: Acetylcholine; ECL: Enterochromaffin-like.

Type I gastric NETs are characterized by their association with atrophic gastritis[31]. This destruction of gastric parietal cells is an often immune-mediated process that results in hypo- or achlorhydria. This process can also be caused by Helicobacter pylori[32]. As a result of decreased gastric acid, there is a positive feedback loop that stimulates the secretion of gastrin. Thus, ECL cells are hyperstimulated by high gastrin levels and this can result in hypertrophy and neoplasia[33]. In contrast, type II G-NETs are often associated with syndromes like sporadic gastrinomas or MEN-1 related Zollinger-Ellison syndrome in which gastrin is autonomously hypersecreted by a gastrinoma in the small bowel or pancreas. Given the ectopic secretion, negative feedback loops are unable to inhibit the release of gastrin even in the presence of high gastric acid, and thus ECL cells are hyperstimulated, ultimately giving rise to type II tumors[28,34].

In comparison, type III carcinoids occur sporadically and have predominantly been noted to be gastrin-independent without associated conditions. Some have also suggested the classification of type IV gastric NETs; these tumors have been described as those that behave similarly to type III as often solitary and aggressive, but with characteristics of NECs rather than NETs. Another description of type IV tumors is with an inherent defect in acid secretion by parietal cells, effectively presenting like type I tumors[35-38]. An additional proposal of type IV carcinoid is as a non-ECL derived neuroendocrine tumor that rather arises from other endocrine cells (e.g. serotonin-, gastrin-, or adrenocorticotrophic hormone)[39]. A recent paper suggested a connection between type IV tumors and PPI use, however this association remains unclear[40]. For the purposes of this review, we will focus on the treatments of types I-III as defined by the WHO[10,11].

Gastric neuroendocrine tumors can present with general signs and symptoms of gastric cancer such as weight loss, abdominal pain, nausea, vomiting, and gastrointestinal bleeding, as NETs represent a subset of gastric cancers. Specifically, type I gastric carcinoids are generally low-grade, slow-growing tumors that have a malignancy risk of less than 3%[41]. Because of their indolent nature, they are often asymptomatic and predominantly discovered incidentally on endoscopy. If the tumor is symptomatic, it can cause abdominal pain, bleeding and vomiting due to the mass effect of the lesion. They are associated with a high survival rate, comparable to the 5-year survival rate of the general population[39]. Type II tumors have a higher rate of spread than type I carcinoids with a 10%-30% chance of metastasis[42]. These tumors have a 5-year survival of roughly 70%. Type II G-NETs can often present with symptoms from Zollinger-Ellison syndrome and increased gastric acid secretion leading to acid reflux, peptic ulcers, abdominal pain and diarrhea[21,43].

In contrast, type III gastric carcinoids are known as the most aggressive subtype with the highest malignant potential and lowest survival rate[44]. Type III carcinoids tend to only show symptoms once the disease is advanced. Patients’ symptoms associated with G-NET tumors themselves are usually nonspecific abdominal pain, nausea, vomiting, gastrointestinal bleeding, and weight loss[24]. Rarely, patients will present with carcinoid syndrome, especially in cases of liver metastases or widespread aggressive disease. Localized tumors drain via the portal system into the liver, where serotonin is metabolized prior to causing symptoms. In contrast, when aggressive metastatic disease is present, serotonin metabolism bypasses the liver (e.g. via hepatic metastasis). Patients with this syndrome may experience flushing, palpitations and diarrhea because of increased circulating serotonin. Additionally, carcinoid syndrome may be associated with right-sided valvular disease, and thus patients may experience symptoms of cardiac disease[45,46].

DIAGNOSIS AND STAGING

Endoscopy

The diagnosis of gastric carcinoid tumors typically begins with an upper endoscopy (esophagogastroduodenoscopy, or EGD) for direct visualization of the gastric mucosa, which also enables the biopsy of any suspicious lesions. Often times, gastric carcinoid tumors, especially type I, are noted incidentally during endoscopies for a different indication. During endoscopy, gastric carcinoids often appear as small, polypoid, or nodular lesions that are frequently found in the gastric body and fundus[47]. It is important that diagnostic endoscopies include data on location, size, appearance, and number of lesions[48]. In some cases, multiple lesions may be present, particularly in type I and type II carcinoids, which are associated with gastrin-driven hyperplasia. In some cases, endoscopic ultrasound (EUS) is used to assess the depth of invasion into the gastric wall and determine if there is lymph node involvement, which helps guide treatment decisions as will be later discussed[49].

Once a lesion is identified, diagnosis is made with histopathologic examination of the biopsy samples. Immunohistochemical staining can confirm the neuroendocrine origin of the tumor, with markers such as chromogranin A and synaptophysin[50-52]. Other tumor markers to consider include cytokeratin, CDX2, and CD56[50,53]. The Ki-67% index and mitotic rate may also help to determine the tumor's grade, further aiding in risk stratification[54]. The Ki-67% of a tumor indicates the rate at which cells are proliferating in a tumor. Higher Ki-67% values indicate a higher mitotic index with more cellular proliferation. According to WHO grading, grade 1 (G1) carcinoids have a Ki-67% of less than 3%. Grade 2 (G2) tumors have a Ki-67% between 3% and 20%, and grade 3 (G3) tumors have a Ki-67% of greater than 20%[10,11,40,50].

Lab testing

Laboratory tests can assess biochemical markers associated with neuroendocrine activity. Serum chromogranin A is the most utilized biomarker typically elevated in gastric carcinoids, especially in type I and type II tumors[55]. With suspected type II carcinoids, fasting serum gastrin levels should be measured, as this elevation seen in gastrinoma-associated Zollinger-Ellison syndrome drives ECL cell hyperplasia and tumor formation[28,34]. Gastrin levels are often elevated in the context of atrophic gastritis in type I tumors. However, these patients are often on proton pump inhibitors which alter levels of both serum markers, so ideally patients should discontinue their PPI for at least 2 weeks prior to testing as to not skew the result[56,57].

Imaging and staging

For staging and metastatic evaluation, cross-sectional imaging such as computed tomography or magnetic resonance imaging of the abdomen and pelvis is performed to assess tumor burden and organ involvement[58]. Additionally, somatostatin receptor imaging, such as a Gallium-68 DOTATATE positron emission tomography (PET) scan, is highly sensitive for detecting metastatic disease since many gastric carcinoids overexpress somatostatin receptors[59]. This advanced imaging modality can help guide treatment decisions, including the use of systemic therapies such as somatostatin analogs (e.g. octreotide) to control hormone secretion and tumor growth[60]. In cases of widespread or aggressive disease where tumors may lose somatostatin receptor expression, fluorodeoxyglucose PET scans may be used to identify metabolically active, poorly differentiated tumors that may require more aggressive treatment strategies[39].

Various classification systems exist for staging. One example is the American Joint Committee on Cancer staging criteria, which uses the tumor-node-metastasis (T-N-M) staging model. Stage I and II encompass tumors with limited local invasion, without nodal or distant metastases. Stage I denotes patients with smaller tumors (< 1.0 cm) with limited local depth invasion (into lamina propria or submucosa) (T1). Stage II includes tumors that are larger (> 1.0 cm) and more invasive (across the lamina propria and/or submucosa or invades muscularis propria) (T2). In addition, stage II also includes more invasive T3 tumors, which have grown through the muscularis propria into the subserosa. Stage III encompasses any tumors that extend deeper into the serosa or visceral peritoneum (T4) or that has spread to nearby lymph nodes (N1). The most widespread disease is stage IV, which includes metastatic tumors that spread to more distant parts of the body[61].

MANAGEMENT

Given the complex pathophysiology and rarity of this disorder, as previously described in this review, managing these patients is a multi-disciplinary initiative consisting of medical oncologists, endocrinologists, gastroenterologists (including advanced endoscopists), pathologists, and surgeons. The clinical decision-making of these tumor boards is typically guided by the subtype of G-NET and more specifically on tumor grade and size[39,62]. While management strategies are highly individualized and often dependent on surgical clinical judgment, we will discuss guidelines and overarching strategy that guide treatment.

Type I G-NETs

The management of type I mainly consists of endoscopic resection and surveillance for smaller (< 1.0 cm), low-grade tumors (G1 or low G2). More extensive resection or surgical consideration is reserved for larger (> 2.0 cm) tumors or those with high-risk features or grade (G3 or high G2), as per The North American Neuroendocrine Tumor Society (NANETS) among others’ recommendation[63,64]. If several small tumors are not amenable to resection or if there is recurrent disease, patients will often be initiated on somatostatin-analog therapy[64,65]. For smaller singular or few tumors, a complete resection (R0) should be performed. If there is an incomplete resection (R1), then the next steps depend on the grade; for low-grade, an endoscopic resection should be repeated, vs higher-grade tumors require surgical resection, as suggested by the European Neuroendocrine Tumor Society’s (ENETS) “step-up approach”[64].

For intermediate size (1.0-2.0 cm) tumors, ENETS suggests EUS to assess depth and local lymph node involvement[64]. If the tumor extends to the muscular layer or there is confirmed lymph node involvement on EUS, then upfront surgical resection is recommended. For these high-risk G2 type I G-NETs, it is recommended to start with a limited resection with sampling of local lymph nodes; however, if a patient has known metastases, then more aggressive upfront gastrectomy (consider subtotal vs total based on location) with D2 Lymphadenectomy may be recommended[64]. Otherwise, an intermediate size tumor is treated like a smaller G1 tumor, and the next steps depend on R0 vs R1 status (Figure 2). In terms of surgical resection for type I tumors, patients benefit from the inclusion of an antrectomy, as the elimination of gastrin-secreting cells ceases the source of gastrin[66,67].

Figure 2 Management of localized gastric neuroendocrine tumors type I tumors. This diagram provides a roadmap for the management of type I gastric neuroendocrine tumors, which are the most common and typically the most benign subtype. This is an original figure. EUS: Endoscopic ultrasound; G-NET: Gastric neuroendocrine tumor.

Type II G-NETs

Given that type II tumors are fed by gastrinomas, treatment of type II tumors begins with addressing the gastrinoma, as this type of G-NET has been noted to regress if its gastrin supply is impeded by somatostatin analogs or surgery[68]. The gold standard for resecting gastrinomas, most commonly found in the duodenum or head of the pancreas, is a pancreaticoduodenectomy (Whipple procedure). If a patient is not a candidate for a Whipple, then a more localized surgical resection or endoscopic excision can be attempted for cytoreduction[3,63]. Otherwise, the best option is medical therapy with a somatostatin analogue for these gastrin-dependent tumors[68].

Type III G-NETs

Type III tumors are the most aggressive tumors and thus require the most invasive management. Depending on the size, location, and invasiveness, there are different extents of resection offered. A surgeon will need to decide the extent of gastric resection required (wedge vs subtotal vs total gastrectomy) and the extent of lymph node sampling that is required. With improvements in endoscopic resection, now in select patients less invasive endoscopic resection or wedge resection can be performed if the tumor has favorable low-grade (G1/G2) and is small (< 1.0-1.5 cm)[64,69]. This is especially true in cases where extensive surgery would be particularly high risk. The role of wedge resection in cases of intermediate grade (G2) type III or intermediate size 1.0-2.0 cm tumors are still debated topics. While subtype is important, prior research and newer evidence confirm the impact that size and grade have on prognosis and thus these qualities guide how aggressive surgery should be[62].

For high-grade (G3) tumors, radical resection with subtotal or total gastrectomy with lymphadenectomy should be performed, as suggested by organizations like NANETS and ENETS[64,70] (Figure 3). This aggressive approach is especially important in high-grade G3 (Ki67 > 20%), metastatic disease, or large tumor (> 2.0 cm) cases[64]. Radical surgical resection may also be required subsequently after a limited wedge resection if postoperative pathology shows nodal metastasis, higher tumor grade than the original biopsy, lymphovascular invasion, or incomplete resection (R1)[69]. In terms of neoadjuvant or adjuvant therapy for these patients, there is no consensus within the community[71].

Figure 3 Management of type III gastric neuroendocrine tumors. This diagram shows the decision-making involved in management of the most aggressive subtype of gastric neuroendocrine tumors, type III. These pathways are adapted from the European Neuroendocrine Tumor Society 2023 Guidelines. This is an original figure. EUS: Endoscopic ultrasound; G-NET: Gastric neuroendocrine tumor.

Metastatic disease

If there are isolated hepatic metastases with localization to one lobe, patients may be treated with hepatic resection, as both symptoms and survival have been shown to improve after[63,72,73]. Gastrointestinal NET metastases to the liver can also be treated with hepatic ablation or radioembolization in conjunction with or without hepatic resection, to ideally treat > 90% of bulk of disease[73-76]. However, it should be noted that much of this evidence is in the context of gastrointestinal NETs in general, not specifically gastric carcinoid given the rare nature of these tumors.

Patients with widespread metastatic disease may also benefit from somatostatin-analog therapy, peptide receptor radionuclide therapy (PRRT), or chemotherapy. Somatostatin analogs, such as octreotide LAR and lanreotide, can help symptoms and slow the growth of well-differentiated tumors[77]. There is data that suggesting that these agents may improve disease-free survival as well[78].

PRRT is performed with beta-emitting radionuclides such as 177 Lutetium (177 LuDOTATATE). Recent prospective randomized control trials have shown great promise with mid-gut NET tumors and gastroenteropancreatic tumors in general (including stomach), in NETTER-1 and NETTER-2, respectively[79-81]. Similar to PPRT-based studies, there is lacking data for the treatment of systemic chemotherapy for specifically gastric neuroendocrine tumors; however, studies of broader gastroenteropancreatic tumors have examined the use of chemotherapy[63]. Agents including 5-fluorouracil, doxorubicin, and streptozocin have been used to treat metastatic pancreatic endocrine tumors, while other studies suggest a potential role for capecitabine, oxaliplatin, and temozolomide for patients with progressive digestive neuroendocrine carcinoma disease[70,82-85]. Everolimus, an mTOR inhibitor, is an additional agent which has been shown to have antitumor effects in advanced NETs when given with octreotide LAR in a phase II trial; however its use with carcinoid syndrome has not been established[86]. As per the most recent National Comprehensive Cancer Network guidelines for metastatic neuroendocrine tumors of the gastrointestinal tract, the preferred regimens include: Cabozantinib (if prior treatment with everolimus or lutetium Lu 177 dotatate), everolimus, PRRT with lutetium Lu 177 dotatate, octreotide, and lanreotide[85].

Perioperative considerations

While carcinoid syndrome is not common with gastric NET tumors, it is important that surgeons are aware of this syndrome and the potentially life-threatening complications that can occur as a result of carcinoid crisis, and how to avoid it. Providers should obtain a careful history to inquire about any carcinoid symptoms[87]. If the patient is experiencing associated diarrhea, electrolyte and vitamin levels should be assessed and corrected. If there is concern for carcinoid syndrome preoperatively, a 5-hydroxyindoleacetic acid (5-HIAA) level should be obtained, as a high 5-HIAA, chromogranin A, and tumor burden have each been correlated with increased risk of experiencing carcinoid crisis[88,89]. Minor procedures, severe emotional stress, anesthesia induction, or tumor manipulation (during physical exam or surgery) can prompt a carcinoid crisis. Patients may show signs such as labile blood pressure, alongside flushing, hyperthermia, or bronchospasm[90]. Ideally, this syndrome or crisis is avoided by preemptively giving octreotide (a somatostatin analogue), which by mimicking the action of the hormone prevents its endogenous release. However, the exact dosage and regimen of octreotide for this indication has not yet been established[90,91]. If an acute episode occurs, intravenous octreotide should be given acutely[87,91]. While initially thought to be inferior to octreotide, emerging evidence also suggests that the use of vasopressors may result in quicker resolution of crisis during intraoperative carcinoid crisis[92]. Future studies should elucidate the role for perioperative octreotide in the prevention and management of carcinoid crisis.

CONCLUSION

Gastric carcinoid is a rare disease but is nonetheless increasing in incidence, largely due to the rise in endoscopic diagnosis. As the disease is more widely diagnosed, further studies have deepened our understanding of pathophysiology, management, and prognosis. Continually updated guidelines provided by organizations like NANETS and ENETS are immensely helpful in guiding medical and surgical management. Nonetheless, there are still gaps in our knowledge, especially in establishing optimal surgical decision-making for type III intermediate grade and medium-sized tumors and in clarifying indications for systemic therapies specifically for gastric NETs. Future work should also elucidate prevention and treatment of carcinoid crisis in perioperative patients. While great strides have been made in the past century since carcinoid was first named, we continue to work towards clarifying optimal care for these patients.