Histopathology, hormone products, and clinicopathological profile of endocrine tumors of the upper small intestine: A study of 44 cases

Neuroendocrine Tumors (NETs) of the Minor Papilla/Ampulla: Analysis of 16 Cases Underlines Homology With Major Ampulla NETs and Differences From Extra-Ampullary Duodenal NETs

Neuroendocrine tumors (NETs) of the minor papilla/ampulla (MIPA) are rare and poorly studied. Only individual case reports and no comprehensive analysis are available from the literature. We collected 16 MIPA NETs and investigated their clinicopathologic and immunohistochemical features, including markers such as somatostatin, pancreatic polypeptide, gastrin, serotonin, MUC1, cytokeratin 7, and somatostatin receptors type 2A and 5. The median age at diagnosis was 57.5 years, and the female-to-male ratio was 2.2:1. The median NET size was 1.45 cm, and most (94%) were low-grade (G1) tumors. Similarly to what was observed in the major ampulla, 3 histotypes were found: (i) ampullary-type somatostatin-producing tumors (ASTs, 10 cases), characterized by somatostatin expression in most tumor cells, focal-to-extensive tubulo-acinar structures, often with psammoma bodies, MUC1 reactivity, and no or rare membranous reactivity for somatostatin receptor type 2A; (ii) gangliocytic paragangliomas (3 cases), characterized by the coexistence of 3 tumor cell types: epithelioid, often reactive for pancreatic polypeptide, ganglion-like cells, and S100 reactive sustentacular/stromal cells; and (iii) ordinary nonfunctioning NETs (3 cases), resembling those more commonly observed in the extra-ampullary duodenum. Comparable histotypes could also be recognized among the 30 MIPA NETs from the literature. No NET-related patient death among MIPA cases was observed during a median follow-up of 38 months; however, MIPA ASTs showed lymph node metastases and invasion of the duodenal muscularis propria or beyond in 44% and 40% of cases, respectively. In conclusion, MIPA NETs closely resemble tumors arising in the major ampulla, with predominance of ASTs.

Four Neuroendocrine Tumor Types and Neuroendocrine Carcinoma of the Duodenum: Analysis of 203 Cases

BACKGROUND

Several types of neuroendocrine neoplasms (NENs) have been described in the duodenal tract, from low-grade tumors (NETs) to high-grade neuroendocrine carcinomas (NECs). A comprehensive analysis of histology, hormonal profile and prognostic parameters of a sufficiently large duodenal NEN series to cover all main kinds of neoplasms is however lacking.

METHODS

We collected a retrospective series of 203 duodenal wall and ampullary region NENs, from six specialized endocrine pathology centers. All were characterized histopathologically and histochemically, and 190 were followed for a median of 9 years.

RESULTS

Twenty-seven poorly differentiated NECs, mostly from the ampullary region, were identified and shown to lead to patient demise in a median of 10 months. Among 176 NETs, four subtypes were characterized, including 20 gastrinomas, 37 ampullary-type somatostatin-producing NETs (ASTs), 12 gangliocytic paragangliomas (GPs) and 106 nonfunctioning NETs (nfNETs). ASTs and GPs were mostly localized in the ampullary/periampullary region, while gastrinomas and nfNETs were mainly from the proximal duodenum. ASTs and gastrinomas showed high rates of local infiltration (especially lymphoinvasion and deep duodenal wall/pancreatic tissue invasion) and lymph node metastasis, while nfNETs had significantly lower and more size-dependent local invasive potential. Disease-specific survival differed significantly between NETs and NECs, though not among NET subtypes. NET cases with distant metastases (n = 23) were significantly associated with larger size, higher proliferative grade, lymphovascular invasion, deep invasion and local lymph node metastasis.

CONCLUSION

Our careful analysis of a large series of duodenal NENs identified five histologically and prognostically different histotypes of potential clinical relevance.

Syndromic versus non-syndromic sporadic gastrin-producing neuroendocrine tumors of the duodenum: comparison of pathological features and biological behavior

Sporadic gastrin-producing neuroendocrine tumors of the duodenum present either with the Zollinger-Ellison syndrome (ZES) or with unspecific symptoms. While syndromic gastrin-producing neuroendocrine tumors often show metastases at the time of diagnosis, those without a syndrome do not. The aim of the study was to search for clinicopathological features that may distinguish the two categories of gastrin-producing duodenal tumors. In a retrospective study, we analyzed the clinical and pathological data in a series of 41 patients with syndromic (i.e., gastrinomas) or non-syndromic duodenal gastrin-producing neuroendocrine tumors (ns-gas-NETs). Twenty-four (59 %) of the 41 patients had tumors that were associated with a ZES and were classified as gastrinomas. These tumors showed a higher Ki-67 index than that of the ns-gas-NETs (1.74 vs. 0.85 %, p = 0.012). In addition, they had more lymph node metastases (75 vs. 6 %, p < 0.001) and showed liver metastases and thus presented much more frequently in TNM stage ≥III (75 vs. 6 %; p < 0.001) than their non-syndromic counterparts. Gastrinomas were removed surgically, ns-gas-NETs endoscopically. We did not observe any significant differences in overall survival or recurrence of disease. Duodenal gastrinomas show no clear morphological features that distinguish them from their non-syndromic counterparts. However, the patients with gastrinomas present in a more advanced stage of disease and need surgical treatment, while non-syndromic gastrin-producing duodenal NETs may be cured by complete endoscopical removal.

Histogenesis and natural history of gut neuroendocrine tumors: present status

Important progress has been made during the last decade in the histopathologic characterization and overall prognostic evaluation of gut neuroendocrine tumors. However, some issues like tumor histogenesis, typing, functional characterization, and preferred site of origin deserve further clarification. This is a survey of the present status of the matter outlining some of the open points. In particular, careful comparison of normal gut endocrine cell types with related endocrine tumors so far identified shows an unexplained lack of neoplasms involving upper small intestine cells like secretin, cholecystokinin, motilin, and GIP cells, as well as the equally unexplained concentration of serotonin EC cell tumors in the ileum and appendix or of somatostatin cell tumors in the duodenal papillary region, despite their wide distribution in the normal gut, not to mention gastrinomas arising in the pancreas, normally devoid of gastrin cells. Special functional (e.g., achlorhydria-driven hypergastrinemia) or pathologic (as chronic inflammation) conditions may locally influence the proliferative and differentiation state of the endocrine cells thus promoting tumor growth. Tumor histologic structure, differentiation level, and proliferative index as well as gastrointestinal wall barriers to tumor diffusion may account for most prognostic parameters, with considerable changes, however, according to the tumor type and site. Thus, further work is needed to develop tumor- and site-adjusted prognostic parameters.

Hyperplasia to neoplasia sequence of duodenal and pancreatic neuroendocrine diseases and pseudohyperplasia of the PP-cells in the pancreas

Hyperplastic changes of the neuroendocrine cell system may have the potential to evolve into neoplastic diseases. This is particularly the case in the setting of genetically determined and hereditary neuroendocrine tumor syndromes such as MEN1. The review discusses the MEN1-associated hyperplasia-neoplasia sequence in the development of gastrinomas in the duodenum and glucagon-producing tumors in the pancreas. It also presents other newly described diseases (e.g., glucagon cell adenomatosis and insulinomatosis) in which the tumors are (or most likely) also preceded by islet cell hyperplasia. Finally, the pseudohyperplasia of PP-rich islets in the pancreatic head is defined as a physiologic condition clearly differing from other hyperplastic-neoplastic neuroendocrine diseases.

Ectopic duodenal insulinoma: a very rare and challenging tumor type. Description of a case and review of the literature

Although most insulinomas are located in the pancreas, very rare ectopic cases have been described in the spleen, perisplenic tissue, duodenohepatic ligament, and adjacent to the ligament of Treitz. Moreover, three cases located in the duodenum have also been reported in the English literature. Ectopic insulinomas represent challenging neoplasms with clinical implications mainly due to the difficulties in their pre-operatory diagnosis and localization. In the present paper, we describe the fourth ectopic duodenal insulinoma so far reported. A 75-year-old woman presented at clinical observation due to neuroglycopenic symptoms that disappeared after glucose intake. Tumor was localized in the second portion of the duodenum in front of the papilla of Vater and was surgically enucleated. Microscopically, it was composed of monomorphic cells with eosinophilic cytoplasm arranged in trabecular and lobular patterns and diffusely positive for insulin, proinsulin, amylin, and PDX1. About 30 % of tumor cells also showed immunoreactivity for somatostatin, while no positivity for glucagon, pancreatic polypeptide, gastrin, serotonin, and somatostatin receptor subtype 2A was found. The Ki67 proliferative index was 1 %. We have also reviewed the literature on this topic to give the reader a comprehensive overview of this very rare tumor type.

Guidelines for biomarker testing in gastroenteropancreatic neuroendocrine neoplasms: a national consensus of the Spanish Society of Pathology and the Spanish Society of Medical Oncology

The annual incidence of neuroendocrine tumours in the Caucasian population ranges from 2.5 to 5 new cases per 100,000 inhabitants. Gastroenteropancreatic neuroendocrine tumours is a family of neoplasms widely variable in terms of anatomical location, hormone composition, clinical syndromes they cause and in their biological behaviour. This high complexity and clinical heterogeneity, together with the known difficulty of predicting their behaviour from their pathological features, are reflected in the many classifications that have been developed over the years in this field. This article reviews the main tissue and clinical biomarkers and makes recommendations for their use in medical practice. This document represents a consensus reached jointly by the Spanish Society of Medical Oncology (SEOM) and the Spanish Society of Pathology (SEAP).

Classification and pathology of gastroenteropancreatic neuroendocrine neoplasms

Gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs) are composed of cells with a neuroendocrine phenotype. The old and the new WHO classifications distinguish between well-differentiated and poorly differentiated neoplasms. All well-differentiated neoplasms, regardless of whether they behave benignly or develop metastases, will be called neuroendocrine tumours (NETs), and graded G1 (Ki67 <2%) or G2 (Ki67 2-20%). All poorly differentiated neoplasms will be termed neuroendocrine carcinomas (NECs) and graded G3 (Ki67 >20%). To stratify the GEP-NETs and GEP-NECs regarding their prognosis, they are now further classified according to TNM-stage systems that were recently proposed by the European Neuroendocrine Tumour Society (ENETS) and the AJCC/UICC. In the light of these criteria the pathology and biology of the various NETs and NECs of the gastrointestinal tract (including the oesophagus) and the pancreas are reviewed.

Pathology of gastrointestinal disorders

Nonneoplastic and neoplastic proliferative lesions of endocrine cells of the gastrointestinal tract are detailed. A multistep continuum from hyperplasia, dysplasia to neoplasia is identified for histamine-producing enterochromaffin-like (ECL) cells of the gastric corpus. Most gastric neuroendocrine tumors (NETs) are silent and composed by ECL cells, the second most frequent neuroendocrine neoplasms being the high-grade neuroendocrine carcinoma (NEC). In the duodenum, preneoplastic lesions are similarly described for gastrin (G) and somatostatin (D) cells. G-cell NETs are the most frequent neuroendocrine tumors of the duodenum, either functioning or nonfunctioning, followed by D-cell NETs and gangliocytic paraganglioma (GCP). No systematic definition of nonneoplastic lesions exists for endocrine cells of the ileum, appendix, and colon-rectum. The most frequent ileal NETs are serotonin-producing enterochromaffin (EC)-cell NETs (classic carcinoid), associating with functional syndrome only in presence of liver metastases. Neoplasms are usually larger in the colon as compared with the small lesions observed in the rectum. High-grade NECs are observed in the colon and rectum-sigmoid, often associate with nonendocrine neoplastic components, and fare an aggressive course with poor outcome and short survival.

Endocrine precursor lesions and microadenomas of the duodenum and pancreas with and without MEN1: criteria, molecular concepts and clinical significance

Proliferative changes in the neuroendocrine cells that precede neoplasia are of interest for the understanding of tumorigenesis and the early recognition of neuroendocrine tumors. This review focuses on precursor lesions of duodenal and pancreatic neuroendocrine tumors in multiple endocrine neoplasia type 1 (MEN1) and also discusses 2 new disease entities of pancreatic microadenomatosis. The gastrinomas observed in MEN1 are almost exclusively localized in the duodenum and are multicentric. It has been shown that, in contrast to sporadic duodenal gastrinomas, they are associated with hyperplastic gastrin cell lesions and tiny gastrin-producing microtumors less than 500 microm in diameter. In the pancreas, microadenomatosis (multiple tumors up to 5 mm in diameter) is a feature of MEN1. These microadenomas predominantly express glucagon and pancreatic polypeptide, but do not cause a hormonal syndrome. Approximately 50% of MEN1 minigastrinomas in the duodenum and almost all microadenomas in the pancreas show allelic deletion of the MEN1 gene and therefore may represent 'initial' neoplasms. In contrast, endocrine cell precursor lesions retain heterozygosity. Pancreatic microadenomatosis was also found unassociated with hereditary syndromes and 2 monohormonal types were identified: (1) glucagon-producing microadenomatosis and (2) insulin-producing microadenomatosis, both associated with macrotumors. Whether these types of microadenomatosis represent novel disease entities and how to diagnose and treat these patients remains to be clarified by further studies.

Site-specific biology and pathology of gastroenteropancreatic neuroendocrine tumors

The gastroenteropancreatic neuroendocrine tumors (GEP-NETs) are composed of cells with a neuroendocrine phenotype. Well-differentiated tumors, well-differentiated carcinomas, poorly differentiated carcinomas, functioning tumors (with a hormonal syndrome), and nonfunctioning tumors are identified. To predict their clinical behavior, these neuroendocrine tumors are classified on the basis of their clinicopathological features, including size, local invasion, angioinvasion, proliferative activity, histological differentiation, and metastases, into neoplasms with benign, uncertain, low-grade malignant and high-grade malignant behavior. In addition, a tumor/nodes/metastases classification and a grading system are presented. In the light of these criteria, the various GEP-NET entities are reviewed.

Carcinoid of the ampulla of Vater

Endocrine neoplasms only rarely occur at the ampulla of Vater, comprising mostly carcinoids and malignant carcinoids, as well as few cases of poorly differentiated endocrine carcinomas (small cell carcinomas). Only 105 cases are reported in the literature, most as single case reports. For many years, the neoplasms of the disseminated neuroendocrine cell system of the gastrointestinal tract have been subsumed as 'carcinoids'. Instead, in the latest World Health Organization (WHO) classification published in 2000, it is recommended to distinguish between (i) well-differentiated endocrine tumors (carcinoids); (ii) well-differentiated endocrine carcinomas (malignant carcinoids); and (iii) poorly differentiated endocrine carcinomas (small cell carcinomas). Patients with carcinoid tumors of the ampulla of Vater are very often free of clinical and laboratory findings that belong to the carcinoid syndrome. Approximately 26% of all patients with carcinoid tumor reported in the literature had neurofibromatosis. Besides endoscopic retrograde cholangiopancreatography, endosonography, computed tomography or magnetic resonance imaging may complete the staging approach of this tumor. The Kausch-Whipple procedure or pylorus-preserving pancreaticoduodenectomy is considered the treatment of choice for ampullary, well-differentiated carcinoids >2.0 cm and for ampullary neuroendocrine carcinomas. However, it should be considered that long-term survival of patients with ampullary carcinoids is also reported after local tumor excision (5-year survival rate of 90%). The dilemma is that the differentiation of neuroendocrine tumors cannot be assessed intraoperatively in most cases. Therefore, considering that the 5-year survival rate in patients with neuroendocrine carcinomas of the ampulla of Vater is very low without radical resection, neuroendocrine tumors of the ampulla of Vater without definite histological differentiation should undergo extended surgery.

Prognostic indicators for carcinoid neuroendocrine tumors of the gastrointestinal tract

Factors that determine the clinical course and outcome of patients with gastrointestinal (GI) carcinoid tumors are complex and multifaceted. These include the site of origin within the GI tract, the size of the primary tumor, and the anatomical extent of disease, whether localized, regional, or metastatic to distant sites. The new World Health Organization (WHO) histological classification of endocrine tumors, including carcinoids, represents a significant advance in terms of providing a consistent framework for histopathological interpretation that should facilitate multicenter research on treatment outcomes. Histochemical indicators of a poorer prognosis are the degree of expression of the proliferation protein Ki-67 and the p53 tumor suppressor protein. Adverse clinical indicators are the malignant carcinoid syndrome, carcinoid heart disease, and high concentrations of the tumor markers, urinary 5-HIAA and plasma chromogranin A.

Xenin-immunoreactive cells and extractable xenin in neuroendocrine tumors of duodenal origin

BACKGROUND & AIMS

Xenin is a 25-amino acid peptide produced by specific endocrine cells of the duodenal mucosa. We investigated whether xenin is expressed in neuroendocrine tumors.

METHODS

Seventy-two foregut and midgut neuroendocrine tumors were examined by means of immunohistochemistry, confocal laser microscopy with an antibody against the C-terminus of xenin, and high-pressure liquid chromatography after acidic extraction, assessed by radioimmunoassay.

RESULTS

We found xenin-immunoreactive cells in 23 of 26 duodenal neuroendocrine tumors, including gastrinomas, somatostatinomas, and nonfunctioning and enterochromaffin cell tumors. In these tumors, up to 20% of the endocrine cells were xenin immunoreactive, and xenin immunoreactivity was concentrated in secretory granules. Xenin was coexpressed with chromogranin A. We found no xenin expression in gastrin-, somatostatin-, and serotonin-immunoreactive cells. High-pressure liquid chromatography after acidic extraction revealed 497 +/- 285 pmol of xenin per gram of tissue in 5 duodenal gastrinomas. The other neuroendocrine tumors, such as bronchial carcinoids, gastric enterochromaffin-like cell carcinoids, gastric and ileal enterochromaffin cell carcinoids, insulinomas, and gastrinomas of pancreatic origin, did not contain immunoreactive xenin.

CONCLUSIONS

Xenin is a peptide marker specific to neuroendocrine tumors of the duodenum. This finding may be useful in tumor classification and in the differential diagnosis of neuroendocrine tumors of the upper gut.

Clinicopathological profile as a basis for classification of the endocrine tumours of the gastroenteropancreatic tract

Recent developments in the field of endocrine cell biology and pathology, at both morphologic and molecular levels, are briefly outlined and discussed as a basis for endocrine tumour characterization. The main clinicopathological tools available for the identification and characterization of endocrine tumours are discussed. Based on this, classifications of endocrine tumours of the pancreas and gastrointestinal tract are developed covering most clinical (hyperfunctional syndromes included), pathologic and biological patterns and with special emphasis on tumour prognosis.

Carcinoid tumors of the ampulla of Vater: a comparison with duodenal carcinoid tumors

BACKGROUND

Although ampullary carcinoid tumors (ACs) are often categorized clinically as duodenal carcinoid tumors (DCs), there are distinct clinical and pathologic differences.

METHODS

Clinical, histopathologic, and immunohistochemical features of 12 ACs were compared with those of 53 DCs that did not involve the ampulla.

RESULTS

Patients with AC were ages 28-74 years (mean, 54.9 years); 8 were males and 4 were females. Five were white and three were black; the race of four patients was not known. The size of ACs ranged from 0.2 to 5.0 cm in greatest dimension. There were no significant differences between AC patients and DC patients with respect to male predominance, race, tumor size, and mitotic rate. The insular growth pattern was more common in AC; the cribriform type was more common in DC. Four of 12 ACs contained psammoma bodies, versus none of 53 DCs (P = 0.001). The rate of metastasis was similar in patients with AC (4 of 12, 33%) compared with DC patients (14 of 53, 26%). In DC patients, involvement of the muscularis propria, a size greater than 2 cm, and mitotic activity were significantly correlated with metastatic risk. In AC patients, tumor size and mitotic activity had no correlation with metastatic potential. One AC had features of an atypical carcinoid tumor; there were none in the duodenal group. One-half of patients with AC presented with jaundice versus 7% of patients with DC (P = 0.005). Three patients (25%) with AC had von Recklinghausen disease versus 0 of 53 patients with DC (P = 0.003). Immunohistochemically, tumor cells expressed somatostatin in 67%, serotonin and cholecystokinin in 17%, insulin in 25%, and glucagon and gastrin in 0% of ACs. In contrast, 56% of DCs expressed gastrin (P < 0.001).

CONCLUSIONS

Carcinoid tumors of the ampulla differ clinically, histologically, and immunohistochemically from carcinoid tumors elsewhere in the duodenum.

Expression of the alpha- and beta-subunits of human chorionic gonadotropin by subsets of parathyroid cells in states of hyperparathyroidism

The alpha-subunit of human chorionic gonadotropin (hCG-alpha) has previously been found to be expressed in hyperplasias and tumours of numerous endocrine tissues including all those involved in MEN-I syndrome except the parathyroid glands. In the present immunohistochemical investigation of 86 patients with various states of hyperparathyroidism, expression of hCG-alpha by subsets of parathyroid cells was shown in 46 cases (54 per cent) including all states of hyperparathyroidism investigated: primary adenoma (n = 34, 44 per cent); uraemic secondary hyperplasia (n = 34, 53 per cent); MEN-I (n = 13, 77 per cent); MEN-II (n = 2, 100 per cent); and parathyroid carcinoma (n = 3, 100 per cent). Although the number of parathyroid cells expressing hCG-alpha was in general low, the occurrence of numerous immunoreactive cells appeared to be concentrated in primary adenoma and MEN-I (20 and 33 per cent of positive cases, respectively). No expression was found in ten normal control glands, except for very rare cells in one case. Expression of hCG-alpha was in part associated with that of hCG-beta, which appeared to be more commonly expressed than hCG-alpha in cases of secondary hyperparathyroidism. In separate experiments, Bouin fixation was found to preserve the immunoreactivity of hCG-alpha and hCG-beta better than the formalin fixation used in this study, suggesting that the figures may be underestimates. These immunohistochemical results are in agreement with a previous biochemical study showing hCG-alpha and hCG-beta in extracts of parathyroid tumours and extend to the parathyroid glands the otherwise ubiquitous finding of hCG-alpha expression in MEN-I-related neoplasms.

Metastatic Psammomatous Somatostatinoma of the Pancreas Causing Severe Ketoacidotic Diabetes Cured by Surgery

A case of somatostatin-producing pancreatic tumor associated with severe insulin-dependent diabetes mellitus and ketoacidotic coma is reported. The tumor, a 10-cm expansile mass arising from the pancreatic tail of a 70-yr-old woman, was first detected by ultrasonography, performed because of abdominal pain, and subsequently confirmed by computed tomography and fine-needle tumor aspiration. Pathologic investigation showed a predominantly solid-trabecular structure with scattered microacini and psammomatous bodies. A large proportion of tumor cells expressed somatostatin and/or calcitonin. Following resection of the primary tumor and three peripancreatic lymph nodes with metastases, the patient recovered rapidly from her diabetic syndrome and remained in substantially good health during a subsequent 8-yr follow-up period, without evidence of tumor recurrence.

Endocrine tumors of the small and large intestine

Among endocrine tumors arising in the intestinal tract, midgut argentaffin EC cell carcinoids, duodenal gastrin cell tumors and rectal trabecular L cell carcinoids, in order of decreasing frequency, are those better represented. Together they account for more than 80% of such tumors. Duodenal somatostatin cell tumors, gangliocytic paragangliomas and poorly differentiated neuroendocrine carcinomas, are also well defined tumor entities. The carcinoid syndrome with intermittent flushing, hypotension and diarrhea, and the Zollinger-Ellison syndrome with severe peptic ulcer disease, are the only hyperfunctional syndromes consistently found in association with these tumors. The carcinoid syndrome arises in about 10% of intestinal carcinoids, usually in their advanced metastatic stage. The Zollinger-Ellison syndrome occurs in association with about 40% of gastrin cell tumors, including small intramural growths. Tumor prognosis depends on mode and site of presentation, histology, cell type(s), size, level of invasion, metastases (especially distant metastases) and associated clinical syndrome or background disease.

Three subtypes of gastric argyrophil carcinoid and the gastric neuroendocrine carcinoma: a clinicopathologic study

BACKGROUND

Enterochromaffinlike (ECL) cell carcinoids recently observed in rats stimulated new interest in gastric endocrine tumors arising in humans.

METHODS

Paraffin-embedded sections of 55 endocrine tumor cases were stained with H&E, mucin tests were performed, and immunoperoxidase was used for detecting endocrine markers; 23 cases were also investigated ultrastructurally.

RESULTS

Forty-five argyrophil carcinoids, 9 neuroendocrine carcinomas, and 1 gastrinoma were identified. Three clinicopathologic subtypes of carcinoids were characterized: (1) twenty-eight cases, none metastatic, arose in a background of body-fundus atrophic gastritis and hypergastrinemia; (2) seven cases, 2 locally metastatic, were associated with hypertrophic gastropathy and hypergastrinemia due to multiple endocrine neoplasia/Zollinger-Ellison syndrome; and (3) ten were sporadic cases, 7 of which were deeply invasive, 6 metastatic, and 5 histologically atypical. All carcinoids showed histochemical and ultrastructural patterns of ECL cells. The 9 neuroendocrine carcinomas, all deeply invasive and metastatic, were composed of anaplastic, small- to intermediate-sized cells with high mitotic index and focal necrosis.

CONCLUSIONS

Gastrin-promoted carcinoids represent a benign or low grade tumor disease, whereas sporadic carcinoids and neuroendocrine carcinomas are life-threatening neoplasms, independent of gastrin promotion.