Histologic characterization and improved prognostic evaluation of 209 gastric neuroendocrine neoplasms. Hum Pathol. 2011;42:1373-1384. [PMID: 21531442 DOI: 10.1016/j.humpath.2011.01.018]

Microsatellite unstable gastrointestinal neuroendocrine carcinomas: a new clinicopathologic entity

Gastroenteropancreatic (GEP) neuroendocrine carcinomas (NECs) and mixed adenoneuroendocrine carcinomas (MANECs) are heterogeneous neoplasms characterized by poor outcome. Microsatellite instability (MSI) has recently been found in colorectal NECs showing a better prognosis than expected. However, the frequency of MSI in a large series of GEP-NEC/MANECs is still unknown. In this work, we investigated the incidence of MSI in GEP-NEC/MANECs and characterized their clinicopathologic and molecular features. MSI analysis and immunohistochemistry for mismatch repair proteins (MLH1, MSH2, MSH6 and PMS2) were performed in 89 GEP-NEC/MANECs (six esophageal, 77 gastrointestinal, three pancreatic, and three of the gallbladder). Methylation of 34 genes was studied by methylation-specific multiplex ligation probe amplification. Mutation analysis of BRAF and KRAS was assessed by PCR-pyrosequencing analysis. MSI was observed in 11 NEC/MANECs (12.4%): seven intestinal and four gastric. All but two MSI-cases showed MLH1 methylation and loss of MLH1 protein. The remaining two MSI-cancers showed lack of MSH2 or PMS2 immunohistochemical expression. MSI-NEC/MANECs showed higher methylation levels than microsatellite stable NEC/MANECs (40.6% vs 20.2% methylated genes respectively, P<0.001). BRAF mutation was detected in six out of 88 cases (7%) and KRAS mutation was identified in 15 cases (17%). BRAF mutation was associated with MSI (P<0.0008), while KRAS status did not correlate with any clinicopathologic or molecular feature. Vascular invasion (P=0.0003) and MSI (P=0.0084) were identified as the only independent prognostic factors in multivariate analysis. We conclude that MSI identifies a subset of gastric and intestinal NEC/MANECs with distinct biology and better prognosis. MSI-NEC/MANECs resemble MSI-gastrointestinal adenocarcinomas for frequency, molecular profile and pathogenetic mechanisms.

Clinical features and management of type I gastric carcinoids

Type I gastric carcinoids (TIGCs) are related to chronic atrophic gastritis and are characterized by hypergastrinemia and hyperplasia of enterochromaffin-like cells. TIGCs are the most frequently diagnosed of all gastric carcinoids, accounting for about 70-80 %. Endoscopically, TIGCs are present as small (<10 mm), polypoid lesions or, more frequently, as smooth, rounded submucosal lesions. Histologically, TIGCs arise in the deep mucosa, with some invading the submucosa. Most TIGCs are well-differentiated tumors, with metastasis being rare. Therefore, patients with TIGCs generally have an excellent prognosis. Among the currently available treatment options are total gastrectomy, partial resection, antrectomy, endoscopic resection, and endoscopic surveillance, although no consensus has been reached on their optimal management. Further studies are needed to develop better management options for patients with TIGC.

Prognostic significance of neuroendocrine components in gastric carcinomas

BACKGROUND

Gastric neuroendocrine carcinomas (NECs) and mixed adenoneuroendocrine carcinomas (MANECs) are aggressive tumours but the prognostic significance of a neuroendocrine component in <30% of the tumour remains unclear. Here, the implication of neuroendocrine components in gastric carcinomas was assessed according to proportion.

METHODS

Surgically resected primary gastric carcinomas with neuroendocrine morphology (NEM; n=88) from 2000 to 2012 at Asan Medical Center were retrospectively reviewed. Neuroendocrine differentiation (NED) was defined as immunopositivity for one of three neuroendocrine markers (synaptophysin, chromogranin or CD56) within the NEM area. To validate the prognostic significance of NED, these cases were compared with 650 randomly selected gastric adenocarcinomas without NEM from the same time period.

RESULTS

Gastric carcinomas with NEM were reclassified as NEC (⩾70% NED, n=47), MANEC (30-70% NED, n=10), gastric carcinoma with 10-30% NED (GCNED, n=8) and carcinoma with <10% NED (n=23). The survival rates of patients with ⩾10% NED were significantly poorer than those with <10% NED but no survival difference was observed between NEC and MANEC. In univariate analyses, older age (⩾60years), larger tumour size (⩾4cm), advanced stage group, ⩾10% NED and lymphovascular or perineural invasion were indicative of a poor prognosis. Stage group and ⩾10% NED remained as independent prognostic factors by multivariate analysis.

CONCLUSIONS

A minor proportion (10-30%) of NED should not be overlooked in gastric carcinomas with NEM. NED should be carefully evaluated to predict patient outcomes and plan optimal additional therapies.

Current concepts in the diagnosis and management of type 1 gastric neuroendocrine neoplasms

The vast majority of gastrin-related gastrointestinal neuroendocrine neoplasms (GI-NENs) develop in the context of chronic atrophic gastritis (type 1), a condition closely related to autoimmune thyroid diseases. These neoplasms are defined as gastric NENs type 1 (GNEN1) and have recently been shown to constitute the commonest GI-NENs in a prospective study. GNEN1s are usually multiple and follow a relative indolent course, raising questions regarding the extent that such patients should be investigated and the appropriate therapeutic interventions needed. Recently, a number of consensus statements and guidelines have been published from various societies dealing with the diagnosis and management of GI-NENs. Endocrinologists are among the many different medical specialties involved in GNEN1s diagnosis and management. However, despite recent advances, few randomized trials are available, and thus existing evidence remains relatively weak compared to other malignancies. The purpose of this review is to provide recent evidence along with currently employed modalities addressing the diagnosis, management, long-term follow-up and potential comorbidities of GNEN1s.

Gastric neuroendocrine neoplasms and related precursor lesions

Gastric neuroendocrine neoplasms (NENs) are a heterogeneous group of tumours showing different clinicopathological features and behaviour, implying a wide spectrum of therapeutic options. They are currently classified using the 2010 WHO classification of digestive neuroendocrine neoplasms into G1-neuroendocrine tumours (NETs), G2-NETs, neuroendocrine carcinomas (NECs) and mixed adenoneuroendocrine carcinomas (MANECs). However, most gastric NENs are composed of ECL-cells (ECL-cell NETs) that can be preceded by ECL-cell hyperplastic and dysplastic lesions, whose oncologic potential has not yet been completely elucidated. ECL-cell NETs differ considerably in terms of prognosis depending on the proliferative status and clinicopathological background. The integration of both aspects in the diagnostic pathway may help to better classify tumours in different prognostic categories, especially when diagnosing them in small bioptic specimens. NECs are all poorly differentiated, highly aggressive carcinomas, while MANECs can show different morphological features that are directly associated with different prognoses. Precursor lesions of such carcinomas are not entirely understood. In this review, the clinicopathological features of gastric NENs and related precursor lesions will be described to give the reader a comprehensive overview on this topic.

Benign glandular downgrowth in gastric neuroendocrine neoplasms: a potential mimic of composite tumour

AIMS

We have observed glandular downgrowth in some gastric neuroendocrine tumours (NETs), in which nonneoplastic appearing gastric glands are admixed with submucosal neuroendocrine nests, that could potentially be confused with composite tumours.

METHODS AND RESULTS

We reviewed 68 gastric NETs with at least submucosal invasion, and evaluated associations between glandular downgrowth, clinical parameters (age, gender, NET setting) and tumour characteristics (size, depth of invasion, grade). Controls included 45 duodenal NETs. Glandular downgrowth was present in 28 (41%) gastric NETs but only 2 (4.4%) duodenal NETs (P < 0.0001). It was not related to age, gender, hypergastrinemia (downgrowth present in 43% of NETs arising in autoimmune gastritis, 41% of Zollinger-Ellison syndrome, 36% of sporadic NETs), tumour size, depth of invasion, or grade. Glandular downgrowth was confined to the submucosa even though 12 (18%) gastric NETs invaded muscularis propria. Submucosal gastric glands (pyloric type in 79%, intestinal in 50%, fundic in 29%) showed metaplastic changes similar to overlying mucosa, were usually mitotically inactive (64% of cases lacked mitotic figures), were geographically restricted to the NET, and never metastasized.

CONCLUSIONS

Our findings support the frequent occurrence and nonneoplastic nature of glandular downgrowth in gastric NETs, which should not be mistaken for composite tumours.

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.

Neuroendocrine pathology of the stomach: the Parma contribution

The current knowledge on gastric neuroendocrine pathology essentially developed in the last four decades. The historical evolution of the concepts and of the relevant clinical implications is described from the perspective of a group actively participating in this research domain. The histamine-producing enterochromaffin-like (ECL) cells have been recognized as the leading cell type involved in the most significant alterations of gastric neuroendocrine cells. The trophic stimulus exerted by circulating gastrin has been demonstrated to have a crucial role on proliferative changes of ECL cells through a sequence of hyperplasia-dysplasia-neoplasia described by Solcia et al. (Digestion 41:185-200,1988). The development of ECL cell tumors in rats treated with toxicological doses of inhibitors of gastric acid secretion prompted appropriate anatomoclinical investigations proving the lack of tumor risk in humans when therapeutic dosages of the drugs are used. Moving from the comprehensive concept of gastric carcinoid, different types of neuroendocrine tumors have been identified in the stomach with substantial variations in prognosis and treatment options. In general, ECL cell tumors developed in hypergastrinemic conditions were found to behave better than those originating outside the setting of hormonal stimulation. Pathological features highly predictive of patient survival have been described. The genetic changes involved in tumor development and progression have revealed substantial overlapping with those of neuroendocrine tumors of other foregut derivatives (i.e., pancreas, duodenum, lung) delineating a family of neuroendocrine tumors genetically distinct from those of the distal parts of the digestive system.

High-grade poorly differentiated neuroendocrine carcinomas of the gastroenteropancreatic system: from morphology to proliferation and back

Poorly differentiated neuroendocrine carcinomas (PDNECs) of the gastroenteropancreatic system (GEP) are a heterogeneous group of aggressive malignancies with a high propensity for distant metastases and an ominous prognosis. They have traditionally been divided into small and large cell subtypes on morphological grounds. However, histological diagnosis needs to be supported by immunohistochemistry to avoid possible misdiagnoses either with the more frequent poorly differentiated adenocarcinomas and squamous cell carcinomas or with lymphomas and mesenchymal neoplasms. Although it is well known that GEP PDNECs are associated with a poor prognosis, data from some published studies seem to suggest that there is a fraction of patients with PDNECs who have better survival than expected. GEP PDNECs are currently classified according to the criteria proposed in the 2010 WHO classification. They are simply called neuroendocrine carcinomas (NECs) and are defined by mitotic count >20 × 10 HPF and/or Ki-67 labeling index >20 %. However, a few recent papers have indicated that some NECs, as defined by the 2010 WHO scheme, do not show a poorly differentiated morphology as expected. This category seems to show a better prognosis and, especially, does not respond to cisplatin-based chemotherapy, which represents the goal standard therapeutic approach to high-grade PDNECs. In the present review, the main morphological, immunohistochemical, and prognostic features will be discussed as well as the opportunity to introduce a new category characterized by well to moderately differentiated morphology associated with high proliferation (mitotic count >20 × 10 HPF and/or Ki-67 index >20 %).

The 2010 WHO classification of digestive neuroendocrine neoplasms: a critical appraisal four years after its introduction

This paper briefly illustrates the basis, rules of application, and present outcome of the current World Health Organization (WHO) classification for neuroendocrine neoplasms. Established in 2010 upon the proposal from the European Neuroendocrine Tumor Society (ENETS), the WHO 2010 fostered some definitional changes (most notably the use of neuroendocrine tumor (NET) instead of carcinoid) and indicated the tools of grading and staging. Specific rules for its application were also defined. The data generated from the use of WHO 2010 classification substantially endorsed its rules and prognostic efficacy. In addition, the application demonstrated some issues, among which are the possible re-definition of the cutoff for grading G1 vs G2, as well as the possible identification of cases with somewhat different clinical behavior within the G3 neuroendocrine cancer class. Overall, since the recent introduction of WHO 2010 grading and staging, it appears wise to keep the current descriptors to avoid unnecessary confusion and to generate comparable data. Homogenous data on large series are ultimately needed to solve such issues.

Review article: the investigation and management of gastric neuroendocrine tumours

BACKGROUND

Gastric carcinoids (GCs) or neuroendocrine tumours (NETs) are increasingly identified at endoscopy, and account for 0.6-2% of all gastric polyps identified. The SEER database in the US has demonstrated a rising incidence of gastric NETs amongst all NETs; from 2.2% between 1950 and 1969 to 6.0% between 2000 and 2007.

AIM

To review the literature and assist clinicians in managing patients with GCs.

METHODS

A literature search was conducted through MEDLINE using search terms: gastric, carcinoid, neuroendocrine tumour, therapy, endoscopy, mucosal resection, submucosal dissection. Relevant articles were identified through manual review. The reference lists of these articles were reviewed to include further appropriate articles.

RESULTS

There are three types of GCs with important epidemiological, pathophysiological, histological and endoscopic differences that affect prognosis and management. Type 1 and 2 GCs develop in the context of hypergastrinaemia that originates from achlorhydria in atrophic gastritis and a gastrinoma, respectively. Type 3 GCs occur sporadically and independent of gastrin. The histological type, grade and Ki67 index are used to determine prognosis and direct clinical management. Type 1 GCs >1 cm in size and type 2 GCs should be assessed for invasion beyond the submucosa with EUS prior to endoscopic resection with EMR or ESD. Type 3 GCs should be managed as per recommendations for gastric adenocarcinoma. The treatment of advanced disease is multimodal.

CONCLUSIONS

Patients with gastric carcinoids should be discussed in a specialist neuroendocrine tumour multidisciplinary meeting to ensure all treatment options are explored in localised and advanced disease. Areas of controversy exist that need further research.

25 Years of neuroendocrine neoplasms of the gastrointestinal tract

This paper provides a personal pathologist's view of how neuroendocrine tumors (NET) were perceived and defined in the last quarter of a century. In years when the Helicobacter pylori, omeprazole and the adenoma-carcinoma sequence in colon carcinogenesis significantly impacted on gastrointestinal (GI) pathology daily practice, neuroendocrine neoplasms of the GI tract passed from the original carcinoid definition to the current NET and neuroendocrine carcinoma (NEC) definitions. The development of different concepts, basic tumor biology knowledge, tools for pathology diagnosis and the various World Health Organization (WHO) classifications from 1980 through 2010 are briefly reviewed and discussed.

Grading of neuroendocrine neoplasms: mitoses and Ki-67 are both essential

BACKGROUND

The current WHO classification for neuroendocrine neoplasms (NEN) of the gastrointestinal tract requires Ki-67 and mitotic index for grading. However, both indexes might be conflicting as far as grade is concerned. In this study, we investigate which of the two indexes is most informative to predict survival.

METHODS

We assessed 362 patients with NEN of gastrointestinal (n = 148), pancreatic (n = 29), lung (n = 77), unknown primary site (n = 102) and of miscellaneous (n = 6) origin. Follow-up and proliferative indexes were recorded.

RESULTS

Survival was clearly correlated with both proliferative indexes (p < 0.001). One hundred and nineteen samples (34%) showed discordance in grading between the Ki-67 and the mitotic index, of which 74 (62%) were biopsies and 45 (38%) resection specimens (p = 0.001). In 86% of these cases, survival matched with the highest proliferative index, which was the Ki-67 index in 87% of these cases. Seventeen cases had a mitotic index of 2 (threshold grade 2) and a Ki-67 index of <3% (grade 1). For these cases, survival curve matched that of patients with concordant indexes of grade 1.

CONCLUSION

Grading NEN using two proliferative markers results in discordance between these indexes in one third of cases, more often in biopsy material than in resection specimens. If results are discordant, survival is for the most part associated with the grade of the highest index, for the most part Ki-67. Thus, grading with two proliferative indexes is useful as it highlights cases where one of these indexes may be incongruent.

Gastroenteropancreatic neuroendocrine neoplasms: historical context and current issues

The digestive organs contain a large number of neuroendocrine cells as part of the diffuse neuroendocrine system. Neuroendocrine tumors can occur in every digestive organ. It has long been recognized that this is a diverse group of tumors with very different clinical outcomes; however, well-recognized prognostic parameters had been elusive until recently. Over the years, there have been several different classification schemes, each with different strengths and weaknesses. In an effort to standardize the classification and grading criteria for gastroenteropancreatic neuroendocrine tumors, the current World Health Organization classification includes a histologic grade based on proliferative rate (mitotic rate and Ki67 index) and a TNM stage that varies from organ to organ. The prognostic value of both the grade and stage has been validated in multiple studies. However, several issues remain, including the lack of standardized methods to assess proliferative rate, potential discrepancies between the mitotic count and the Ki67 index; intratumoral heterogeneity in proliferative rate; and the need for refinement in proliferative cut-points to define the grades. More studies are needed to further improve the classification of neuroendocrine tumors, thus guiding optimal treatment for these tumors.

Histologic changes in type A chronic atrophic gastritis indicating increased risk of neuroendocrine tumor development: the predictive role of dysplastic and severely hyperplastic enterochromaffin-like cell lesions

The role of putative preneoplastic enterochromaffin-like cell lesions, either hyperplastic or dysplastic, in the genesis of type 1 enterochromaffin-like cell neuroendocrine tumors associated with type A chronic atrophic gastritis, their actual neoplastic risk, and their precise histogenetic mechanism deserve further clarification by specific histopathologic studies coupled with patient follow-up. A total of 100 patients with severe type A chronic atrophic gastritis, enterochromaffin-like cell hyperplasia, and antral G-cell hyperplasia were endoscopically and histologically followed up for a median of 90.1 months (total of 9118 person-months). Preneoplastic enterochromaffin-like cell lesions and newly developed neuroendocrine tumors were investigated histologically and histochemically, in parallel with enterochromaffin-like cell lesions found in nontumor mucosa of another 32 well-characterized and previously reported type 1 neuroendocrine tumors. Both neuroendocrine and nonneuroendocrine mucosa changes were analyzed and statistically evaluated. During follow-up, 7 of 100 patients developed neuroendocrine tumors: 5 were in a group of 20 cases with previous enterochromaffin-like cell dysplasia and 2 were among 80 cases showing only enterochromaffin-like cell hyperplasia throughout the study (hazard ratio, 20.7; P < .001). The severity of enterochromaffin-like cell hyperplasia at first biopsy, with special reference to linear hyperplasia with 6 chains or more per linear millimeter, also increased the risk of neuroendocrine tumor development during follow-up (hazard ratio, 13.0; P < .001). Enterochromaffin-like cell microinvasive dysplastic lesions arising at the epithelial renewal zone level, in connection with immature proliferating mucous-neck cells, were found to be linked to early intramucosal neuroendocrine tumor histogenesis. Both enterochromaffin-like cell dysplasia and severe hyperplasia indicate increased risk of neuroendocrine tumor development in type A chronic atrophic gastritis with hypergastrinemia/G-cell hyperplasia.

Neuroendocrine proliferations of the stomach: a pragmatic approach for the perplexed pathologist

The classifications of neuroendocrine proliferations that lead from enterochromaffin-like cell hyperplasia to neuroendocrine tumors in the stomach are complicated and relatively inaccessible to nonspecialists. Consequently, these lesions tend to remain widely underdiagnosed until they progress to easily recognizable neuroendocrine tumors. This review provides simple, yet rigorous guidelines on how to recognize, classify, and diagnose the neuroendocrine proliferations found in the stomach, emphasizing the most common background in which they arise, atrophic gastritis. After a succinct outline of the types and distribution of the neuroendocrine cells in the normal gastric mucosa we discuss the most common situations in which the pathologist needs to think about gastric neuroendocrine cells. In general practice gastric biopsy specimens are often numerically and topographically inadequate for the evaluation of atrophic gastritis; therefore, we have included an algorithm to address specifically the steps that should be taken when confronted with suboptimal sampling. Finally, we illustrate the suggested diagnostic process with 4 cases that are fairly representative of the type of situations encountered in everyday practice. The pathologist who follows our simple steps will be better aware of this neglected area of gastric pathology and will learn to suspect, recognize, and accurately diagnose the most common abnormalities of the neuroendocrine system in the stomach.

Achaete-scute homolog 1 as a marker of poorly differentiated neuroendocrine carcinomas of different sites: a validation study using immunohistochemistry and quantitative real-time polymerase chain reaction on 335 cases

Neuroendocrine carcinomas show overlapping morphological and immunohistochemical features independently of their site of origin, which makes identification of the primary location problematic when they are diagnosed as metastases of unknown origin. Neuroendocrine carcinomas are easily morphologically differentiated from neuroendocrine tumors in surgical material, although this distinction can be difficult when using small biopsy specimens. The diagnostic usefulness of different transcription factors as site-specific markers or as discriminating markers between neuroendocrine carcinomas and neuroendocrine tumors has been previously studied with sometimes contradictory results. In this respect, the role of achaete-scute homolog 1 has been poorly investigated, although some recent findings demonstrate its expression in neuroendocrine carcinomas. Using immunohistochemistry and quantitative real-time polymerase chain reaction, we investigated the expression of achaete-scute homolog 1 in 335 neuroendocrine neoplasms (194 neuroendocrine carcinomas and 141 neuroendocrine tumors) of different sites, to check its possible utility as diagnostic marker. High concordance between immunohistochemical and molecular findings was found. Achaete-scute homolog 1 expression was identified in 82% of lung neuroendocrine carcinomas and 70% of extrapulmonary neuroendocrine carcinomas. Achaete-scute homolog 1 was not detected in any gastroenteropancreatic neuroendocrine tumor and was found in only a minority of lung carcinoids. The diagnostic sensitivity and specificity of achaete-scute homolog 1 expression were 82.4% and 89.7% in distinguishing neuroendocrine carcinomas from neuroendocrine tumors of the lung, 40.6% and 100% to differentiate extrapulmonary neuroendocrine carcinomas from neuroendocrine tumors, and 82.4% and 59.4% in distinguishing lung from extrapulmonary neuroendocrine carcinomas. Our data suggest that achaete-scute homolog 1 is not a site-specific marker. However, achaete-scute homolog 1 may be proposed as a diagnostic marker of poor differentiation and may help to differentiate neuroendocrine carcinomas from neuroendocrine tumors in difficult cases.

Histopathology of gastrointestinal neuroendocrine neoplasms

Gastrointestinal neuroendocrine neoplasms (GI-NENs) arise from neuroendocrine cells distributed mainly in the mucosa and submucosa of the gastrointestinal tract. In 2010, the World Health Organization (WHO) classification of NENs of the digestive system was changed, categorizing these tumors as grade 1 neuroendocrine tumor (NET), grade-2NET, neuroendocrine carcinoma (large- or small-cell type), or mixed adenoneuroendocrine carcinoma (MANEC). Such a classification is based on the Ki-67 index and mitotic count in histological material. For the accurate pathological diagnosis and grading of NENs, it is important to clearly recognize the characteristic histological features of GI-NENs and to understand the correct method of counting Ki-67 and mitoses. In this review, we focus on the histopathological features of GI-NENs, particularly regarding biopsy and cytological diagnoses, neuroendocrine markers, genetic and molecular features, and the evaluation of the Ki-67 index and mitotic count. In addition, we will address the histological features of GI-NEN in specific organs.

Gastric and duodenal neuroendocrine tumours

Gastric neuroendocrine neoplasms (NENs) are increasing in frequency and have a varied spectrum with regard to histology, clinicopathologic background, stage, and prognosis. They are usually discovered incidentally, are for the most part benign and are associated with hypergastrinaemia (secondary either to chronic atrophic gastritis or rarely Zollinger-Ellison syndrome; types 1 and 2, respectively) or more rarely sporadic type 3. Applications of recent staging and grading systems - namely using Ki-67 proliferative indices - (from ENETS and WHO 2010) can be particularly helpful in further categorising these tumours. The natural history of Type 1 gastric carcinoids is generally (>95%) favourable and simple surveillance is usually recommended for small (<1 cm) T1 tumours, with local (endoscopic or surgical) resection for larger lesions. Other potential therapies such as somatostatin analogues and gastrin receptor antagonists may offer newer therapeutic possibilities. Rarely, gastric NENs have a malignant course and this is usually confined to Type 2 and especially Type 3 tumours; the latter mimic the biological course of gastric adenocarcinoma and require radical oncological therapies. Most duodenal NENs, apart from gastrinomas (that are not dealt with here) are sporadic and non functional. They are also increasing in frequency probably due to incidental discovery at endoscopy or imaging for other reasons and this may account for their overall good prognosis. Peri-ampullary and ampullary NENs may have a more aggressive outcome and should be carefully appraised and treated (often with surgical resection).

Intervention in gastro-enteropancreatic neuroendocrine tumours

Neuroendocrine tumours require dedicated interventions to control their capacity to secrete hormones but also, antitumour growth strategies. Recommendations for early interventions in NET include the management of hormone-related symptoms and poorly differentiated neuroendocrine carcinomas. In contrast, prognostic heterogeneity is a key feature of well differentiated NET that complexified the antitumour strategy whatever the stage in this subgroup of tumour. In this review, timely therapeutic interventions to control hormone-related symptoms and tumour growth in GEP NET patients are discussed. The necessity of controlling hormone-related symptoms as the first step of any strategy affects also the tumour growth control strategy. In the absence of cure at the metastatic stage, progresses are expected in the recognition of well differentiated NET subgroups that display either excellent or poor prognosis.

Pathology - grading and staging of GEP-NETs

Gastroenteropancreatic neuroendocrine tumours (GEP-NETs) constitute a heterogeneous group of neoplasms. In the last few decades, due to a substantial rise in incidence and prevalence, GEP-NETs have been included among the most common tumours of the gastrointestinal tract. Diagnosis could be challenging and a significant number of patients present with metastatic or unresectable disease. The development of appropriate tools for standardised prognostic stratification and the introduction of effective target therapies have opened new horizons for planning tailored surgical or medical management and follow-up programs for these complex neoplasms. An overview on the GEP-NETs' diagnostic and prognostic criteria proposed by the recently published WHO classification and ENETS and UICC TNM staging systems is presented, focussing on their impact on the clinical and therapeutical approaches.

[Gastrointestinal mixed adenoneuroendocrine carcinomas. An attempt at classification of mixed cancers]

Mixed adenoneuroendocrine carcinomas (MANECs) are a challenge for the diagnostics and the concept of a histogenetic tumor typing. They are classified into three malignant subgroups: high grade malignant MANECs combine an adenoma or adenocarcinoma with a small cell or large cell neuroendocrine carcinoma, intermediate grade malignant MANECs consist of a neuroendocrine tumor (NET grade 1 or 2), often a globlet cell carcinoid and a poorly differentiated adenocarcinoma or diffuse carcinoma of signet ring cell type. The prototype of a low grade malignant MANEC is the globlet cell carcinoid. Molecular analysis indicates a common clonal origin of the different components in MANECs. The prognosis is determined by the most aggressive tumor component. The pathogenesis of MANECs is apparently a sequence of increasing malignant transformation which leads either from an adenoma/adenocarcinoma to a small or large cell neuroendocrine carcinoma or from a neuroendocrine tumor (NET), often a globlet cell carcinoid to a poorly differentiated adenocarcinoma or a diffuse carcinoma of signet ring cell type.

Minute type I gastric carcinoid with regional lymph node metastasis

Type I gastric carcinoids are indolent lesions that only rarely metastasize. Until now, lymph node metastasis had only being observed in large (≥10 mm) and usually invasive lesions (deep submucosa or beyond). This study reports a diminutive (8 mm) gastric carcinoid, limited to the superficial layer of the submucosa (sm1), with no angiovascular invasion, but with a high Ki-67 index (7%) and an involved perigastric lymph node. The aggressive behavior of this lesion ends the previous believe that small and superficial type I gastric carcinoids do not metastasize. This case also indicates that better parameters are necessary to evaluate the malignant potential of these lesions and presents a further support to the value of 2010 World Health Organization classification of gastrointestinal neuroendocrine tumors.

Immunohistochemical consistency between primary tumors and lymph node metastases of gastric neuroendocrine carcinoma

Background

Gastric neuroendocrine carcinoma (G-NEC) is a rare, highly malignant tumor that exhibits aggressive growth leading to vascular invasion, distant metastasis and extremely poor prognosis. We studied the clinicopathological findings of seven patients at our institute to better under this disease.

Methods

Seven cases of G-NEC were identified among 1,027 cases of gastric carcinoma that underwent gastrectomy at Kansai Rousai Hospital between 2002 and 2010. We studied the pathological and immunohistochemical features of gastric neuroendocrine carcinomas at both the primary site and metastatic lymph nodes.

Results

The mean patient age was 73 years (range 63 to 86 years). There were no females in this series. The final staging was Stage I in one case, Stage II in two, Stage III in two and Stage IV in two. A total of 31 metastatic lymph nodes were found in these patients. This study revealed that the ratio of neuroendocrine cells was similar between the primary and metastatic sites, which tended to show the same expression patterns of neuroendocrine markers.

Conclusions

Metastatic lymph nodes showed heterogeneous immunohistochemical expression patterns similar to the primary sites. G-NEC is far advanced at diagnosis and rapidly reaches the lymph nodes retaining its heterogeneity, carrying a worse prognosis than common gastric cancer.

Mini abstract

G-NEC grows rapidly and metastasizes to the lymph nodes, retaining its pathological and immunohistochemical heterogeneity even at the metastatic sites.

Colorectal poorly differentiated neuroendocrine carcinomas and mixed adenoneuroendocrine carcinomas: insights into the diagnostic immunophenotype, assessment of methylation profile, and search for prognostic markers

Colorectal poorly differentiated neuroendocrine carcinomas (NECs) and mixed adenoneuroendocrine carcinomas (MANECs) are well-recognized entities generally known to be associated with biological aggressiveness and poor patient survival. However, a few published papers have highlighted the existence of a subgroup of tumors with a better survival than expected; however, to date, there are no established parameters that usefully identify this category. In the present study we have investigated the morphologic features, the CpG methylator phenotype (CIMP), microsatellite instability (MSI), and the immunohistochemical profile, including the expression of transcription factors (TTF1, ASH1, CDX2, and PAX5), stem cell markers (CD117 and CD34), and cytokeratins 7 and 20, in a series of 39 carcinomas (27 NECs and 12 MANECs) to better characterize such neoplasms and to search for prognostic indicators. No different patient survival was observed between NECs and MANECs. Neoplasms showed a heterogenous spectrum of morphologic and immunohistochemical features; however, only large-cell subtype, significant peritumoral lymphoid reaction, CD117 immunoreactivity, vascular invasion, and MSI/CIMP+ status were significantly correlated with prognosis on univariable analysis. Furthermore, vascular invasion and CD117 immunoreactivity were independent prognostic markers on multivariable analysis. In addition to these prognostic features, neoplasms showed different expression of transcription factors, stem cell markers, and cytokeratins that should be considered for diagnostic purposes and, especially, for discriminating among possible differential diagnoses.

Mixed Adenoneuroendocrine Carcinomas (MANECs) of the Gastrointestinal Tract: An Update

The systematic application of immunohistochemical techniques to the study of tumors has led to the recognition that neuroendocrine cells occur rather frequently in exocrine neoplasms of the gut. It is now well known that there is a wide spectrum of combinations of exocrine and neuroendocrine components, ranging from adenomas or carcinomas with interspersed neuroendocrine cells at one extreme to classical neuroendocrine tumors with a focal exocrine component at the other. In addition, both exocrine and neuroendocrine components can have different morphological features ranging, for the former, from adenomas to adenocarcinomas with different degrees of differentiation and, for the latter, from well differentiated to poorly differentiated neuroendocrine tumors. However, although this range of combinations of neuroendocrine and exocrine components is frequently observed in routine practice, mixed exocrine-neuroendocrine carcinomas, now renamed as mixed adenoneuroendocrine carcinomas (MANECs), are rare; these are, by definition, neoplasms in which each component represents at least 30% of the lesion. Gastrointestinal MANECs can be stratified in different prognostic categories according to the grade of malignancy of each component. The present paper is an overview of the main clinicopathological, morphological, immunohistochemical and molecular features of this specific rare tumor type.

Choice of tumour markers in patients with neuroendocrine tumours is dependent on the histological grade. A marker study of Chromogranin A, Neuron specific enolase, Progastrin-releasing peptide and cytokeratin fragments

BACKGROUND

Chromogranin A (CgA) is the most important tumour marker for well-differentiated neuroendocrine tumours (NET) and neuron specific enolase (NSE) for poorly differentiated neuroendocrine carcinoma (NEC). This study investigated whether the markers progastrin-releasing peptide (proGRP) and cytokeratin fragments (CKfr) CK8, CK18 and CK19 (MonoTotal) can be of additional value to the histological classification and help predict survival in these patients.

METHODS

CgA, NSE, proGRP and CKfr were measured in 242 patients with grade 1 NET (G1NET), 38 with grade 2 NET (G2NET), 42 with large cell NEC (LCNEC), 251 with small cell NEC (SCNEC) and in 282 healthy persons. Results were compared with tumour characteristics and survival by means of Receiver Operating Characteristics (ROC) curves and Cox regression analyses.

RESULTS

The largest area under the ROC curve was for CgA (0.86, 0.91 and 0.90, respectively) when comparing patients with G1NET, G2NET and LCNEC with healthy persons. ProGRP showed the highest sensitivity (73%) at 95% specificity in patients with SCNEC. In a multivariate survival analysis, only CKfr was associated with survival (P<0.0001) for patients with well-differentiated NET (G1NET and G2NET). For patients with poorly differentiated NEC, both CKfr and NSE were associated with survival (P<0.0001 and P=0.003, respectively).

CONCLUSION

Within all histological groups a combination of tumour markers proved to be more informative as diagnostic and prognostic marker than each marker alone. In patients with well-differentiated NET and LCNEC we recommend the use of CgA and CKfr, whilst in patients with SCNEC, proGRP and CKfr are preferred.