Gastric adenocarcinoma and proximal polyposis of the stomach (GAPPS): a new autosomal dominant syndrome

Germline likely pathogenic variants in ataxia-telangiectasia-mutated gene in an Iranian family with hereditary diffuse gastric cancer without CDH1 mutation

Background

Gastric cancer (GC) is the fourth common cancer in the world and the second cause of cancer-related mortality. Germline mutations in the E-cadherin gene (CDH1) are the most common cause of hereditary diffuse GC (HDGC) and explain 25%-30% of cases. In HDGC families without the pathogenic CDH1 variant, there is poor management and therapeutic strategies, and detect other genetic defects in HDGC, except CDH1 gene will be useful for further clarification of the disease mechanisms and risk-reducing strategies. Here, we reported an Iranian pedigree with familial HDGC to assess the fundamental genetic causes by whole-exome sequencing (WES).

Materials and Methods

WES performed in an Iranian with a history of familial GC in whom no pathogenic variants or indels has been found in CDH1 and CTNNA1 genes with Sanger sequencing and multiplex ligation-dependent probe amplification methods.

Results

Prioritizing genes associate with HDGC recognized several variants include c.2572T>C, and c.3161C>G in ataxia-telangiectasia mutated (ATM), c.1114A>C in BRCA2, and finally c.1173A>G in PIK3CA. Protein function prediction software tools reveal that c.3161C>G in ATM is likely pathogen.

Conclusion

The results of this study suggested a role for the known cancer predisposition gene ATM in families with HDGC with no pathogenic variant in CDH1. Our results suggested that mutations in ATM and other genes, particularly the mutations found in this study, should be considered even in one case of positive familial status of HDGC disease. The presence of these mutations in patients with familial history raises important issues regarding genetic counseling.

Advances in the Aetiology & Endoscopic Detection and Management of Early Gastric Cancer

Simple Summary

Gastric adenocarcinoma has remained a highly lethal disease. Awareness and recognition of preneoplastic conditions (including gastric atrophy and intestinal metaplasia) using high-resolution white-light endoscopy as well as chromoendoscopy is therefore essential. Helicobacter pylori, a class I carcinogen, remains the main contributor to the development of sporadic distal gastric neoplasia. Management of early gastric neoplasia with endoscopic resections should be in line with standard indications. A multidisciplinary approach to any case of an early gastric neoplasia is imperative. Hereditary forms of gastric cancer require a tailored approach and individua-lized surveillance.

Abstract

The mortality rates of gastric carcinoma remain high, despite the progress in research and development in disease mechanisms and treatment. Therefore, recognition of gastric precancerous lesions and early neoplasia is crucial. Two subtypes of sporadic gastric cancer have been recognized: cardia subtype and non-cardia (distal) subtype, the latter being more frequent and largely associated with infection of Helicobacter pylori, a class I carcinogen. Helicobacter pylori initiates the widely accepted Correa cascade, describing a stepwise progression through precursor lesions from chronic inflammation to gastric atrophy, gastric intestinal metaplasia and neoplasia. Our knowledge on He-licobacter pylori is still limited, and multiple questions in the context of its contribution to the pathogenesis of gastric neoplasia are yet to be answered. Awareness and recognition of gastric atrophy and intestinal metaplasia on high-definition white-light endoscopy, image-enhanced endoscopy and magnification endoscopy, in combination with histology from the biopsies taken accurately according to the protocol, are crucial to guiding the management. Standard indications for endoscopic resections (endoscopic mucosal resection and endoscopic submucosal dissection) of gastric dysplasia and intestinal type of gastric carcinoma have been recommended by multiple societies. Endoscopic evaluation and surveillance should be offered to individuals with an inherited predisposition to gastric carcinoma.

Novel Genetic Causes of Gastrointestinal Polyposis Syndromes

Hereditary polyposis syndromes are characterized by a large number and/or histopathologically specific polyps in the gastrointestinal tract and a high risk of both colorectal cancer and extracolonic cancer at an early age. While the genes responsible for some of the syndromes, eg, APC in familial adenomatous polyposis and STK11 in Peutz-Jeghers syndrome, have been known for decades, novel genetic causes have recently been detected that have shed light on the broader clinical spectrum of syndromes. Genetic diagnoses are important because they can facilitate a personalized surveillance program. Furthermore, at-risk members of the patient's family can be tested and enrolled in surveillance as needed. In some cases, prenatal diagnostics should be offered. In this paper, we describe the development in germline genetics of the hereditary polyposis syndromes over the last 10-12 years, their clinical characteristics, as well as how to implement genetic analyses in the diagnostic pipeline.

Gastric cancer genetic predisposition and clinical presentations: Established heritable causes and potential candidate genes

Tumour risk syndromes (TRS) are characterized by an increased risk of early-onset cancers in a familial context. High cancer risk is mostly driven by loss-of-function variants in a single cancer-associated gene. Presently, predisposition to diffuse gastric cancer (DGC) is explained by CDH1 and CTNNA1 pathogenic and likely pathogenic variants (P/LP), causing Hereditary Diffuse Gastric Cancer (HDGC); while APC promoter 1B single nucleotide variants predispose to Gastric Adenocarcinoma and Proximal Polyposis of the Stomach (GAPPS). Familial Intestinal Gastric Cancer (FIGC), recognized as a GC-predisposing disease, remains understudied and genetically unsolved. GC can also occur in the spectrum of other TRS. Identification of heritable causes allows defining diagnostic testing criteria, helps to clinically classify GC families into the appropriate TRS, and allows performing pre-symptomatic testing identifying at-risk individuals for downstream surveillance, risk reduction and/or treatment. However, most of HDGC, some GAPPS, and most FIGC patients/families remain unsolved, expecting a heritable factor to be discovered. The missing heritability in GC-associated tumour risk syndromes (GC-TRS) is likely explained not by a single major gene, but by a diversity of genes, some, predisposing to other TRS. This would gain support if GC-enriched small families or apparently isolated early-onset GC cases were hiding a family history compatible with another TRS. Herein, we revisited current knowledge on GC-TRS, and searched in the literature for individuals/families bearing P/LP variants predisposing for other TRS, but whose probands display a clinical presentation and/or family history also fitting GC-TRS criteria. We found 27 families with family history compatible with HDGC or FIGC, harbouring 28 P/LP variants in 16 TRS-associated genes, mainly associated with DNA repair. PALB2 or BRCA2 were the most frequently mutated candidate genes in individuals with family history compatible with HDGC and FIGC, respectively. Consolidation of PALB2 and BRCA2 as HDGC- or FIGC-associated genes, respectively, holds promise and worth additional research. This analysis further highlighted the influence, that proband's choice and small or unreported family history have, for a correct TRS diagnosis, genetic screening, and disease management. In this review, we provide a rational for identification of particularly relevant candidate genes in GC-TRS.

Gastric Adenocarcinoma and Proximal Polyposis of the Stomach in a Hispanic Pediatric Patient With APC Gene Variant c.-191T>G

Gastric adenocarcinoma and proximal polyposis of the stomach (GAPPS) is a rare gastric polyposis syndrome defined by numerous polyps (>100) in the fundus and body of the stomach with sparing of the lesser curvature and antrum. GAPPS is linked to a variant in the promoter 1B region of the APC gene. These variants carry a high risk of developing gastric adenocarcinoma, which can occur at an early age. We report a case of GAPPS discovered in a 16-year-old Hispanic girl after endoscopy detected extensive fundic gland polyposis. Genetic testing revealed a promoter 1B point mutation of the APC gene, variant c.-191T>G. Although similar variants have been reported (i.e., c.-191T>C, c.-195A>C, c.-192A>G) in association with GAPPS, variant c.-191T>G has not nor has GAPPS ever been described in a Hispanic individual before.

Prevalence of Gastroduodenal Polyps in Children With Familial Adenomatous Polyposis

Objective

To assess the prevalence of upper gastrointestinal adenomatous polyps in a cohort of pediatric familial adenomatous polyposis (FAP) patients to determine if early screening is warranted.

Study Design

All 11 pediatric FAP patients diagnosed in Manitoba between January 2012 and December 2019 were recruited. Patient records were examined and data on age of diagnosis, gene mutation, age of first screening endoscopy, number of endoscopies, number of gastric and colonic polyps, associated pathology, medications, symptoms and FAP-related surgeries were extracted and descriptive statistics reported.

Results

A total of 11 children were diagnosed with FAP over the study period with a mean age at diagnosis of 6.3 ± 3.2 years with 72.3% males and median follow-up of 4.8 years. The mean age at first gastroscopy was 10.9 ± 2.9 years and 10.8 ± 3.0 years at colonoscopy. Eight patients (72%) had upper gastrointestinal polyps, with adenomatous changes seen in seven of them on pathology. No patients had invasive carcinoma or high-grade dysplasia. All patients developed tubular adenomas on colorectal polyp pathology. Four (36%) patients underwent surgical colectomy.

Conclusions

Early-onset upper gastrointestinal adenomatous polyps in a pediatric FAP are common. Our study provides further data to support consideration of further, large-scale research into the benefit of early endoscopic screening for upper gastrointestinal malignancy in FAP patients.

Proton Pump Inhibitors and Gastric Cancer

Concerns have been raised regarding the long-term use of proton pump inhibitors (PPIs) as an important risk factor for gastric cancer in clinical practice. PPIs can cause hypergastrinemia at clinical doses, and hypergastrinemia has been reported to induce malignant neoplasms in the stomach in previous animal studies. In humans, the proliferation of enterochromaffin-like (ECL) cells induced by hypergastrinemia is suspected as a potential mechanism of gastric cancer. Meanwhile, persistent Helicobacter pylori (H. pylori) infection causes gastric atrophic change, which itself is a major cause of gastric cancer, and it can further increase the risk of gastric cancer by strengthening corpus atrophy through interaction with PPIs. Recent epidemiologic studies have reported an important link between long-term PPI intake and gastric cancer risk even after successful eradication of H. pylori. However, due to the methodological limitations of observational clinical studies, the causal relationship is still not clear, and a recent big data-based study reported that long-term PPI use was not related to gastric cancer incidence. Taken together, despite the potential detrimental effects of PPIs, it is currently difficult to draw a definite conclusion about its association with gastric cancer. To minimize the possibility of gastric cancer in H. pylori-infected patients or precancerous lesions in long-term PPI users, long-term PPI administration should be limited to the minimum effective dose, and antibacterial treatment for H. pylori should be considered.

A mosaic PIK3CA variant in a young adult with diffuse gastric cancer: case report

Hereditary diffuse gastric cancer (HDGC) is associated with germline deleterious variants in CDH1 and CTNNA1. The majority of HDGC-suspected patients are still genetically unresolved, raising the need for identification of novel HDGC predisposing genes. Under the collaborative environment of the SOLVE-RD consortium, re-analysis of whole-exome sequencing data from unresolved gastric cancer cases (n = 83) identified a mosaic missense variant in PIK3CA in a 25-year-old female with diffuse gastric cancer (DGC) without familial history for cancer. The variant, c.3140A>G p.(His1047Arg), a known cancer-related somatic hotspot, was present at a low variant allele frequency (18%) in leukocyte-derived DNA. Somatic variants in PIK3CA are usually associated with overgrowth, a phenotype that was not observed in this patient. This report highlights mosaicism as a potential, and understudied, mechanism in the etiology of DGC.

High interobserver variability and frequent overdiagnosis of dysplasia in fundic gland polyps can be improved by detecting atypia on the surface epithelium and an abrupt transition to non-neoplastic cells

AIMS

Fundic gland polyps (FGPs) arise sporadically and in combination with familial adenomatous polyposis (FAP). Criteria for distinguishing low-grade dysplasia (LGD) from regenerative atypia in FGPs are not well established. The aims of study were to determine: (i) interobserver variability in diagnosing LGD in FGPs; (ii) bias in diagnosing LGD in FAP patients; and (iii) stringent criteria for LGD in FGPs.

METHODS AND RESULTS

Five senior pathologists who were blinded to the clinical history reviewed 72 FAP-associated FGPs and 34 sporadic FGPs. Cases were classified as negative (score = 0) or positive (score = 1) for LGD. Each case was assigned a 'combined dysplasia score' (CDS) ranging from 0 to 5 to reflect all five opinions. Fleiss' kappa showed only moderate interobserver agreement (κ = 0.46). Forty-one FGPs were classified as negative for dysplasia by consensus (CDS = 0-1), including 10 (24%) originally diagnosed as LGD. In contrast, all 37 cases classified as LGD by consensus (CDS = 4-5) were originally diagnosed as LGD, indicating that overdiagnosis of dysplasia is more common than underdiagnosis (P = 0.0012). Cytological atypia in the surface epithelium and an abrupt transition between atypical and normal-appearing epithelium were the most sensitive (97% and 100%, respectively) and specific (100% and 98%, respectively) features of dysplasia (P < 0.0001 for both comparisons). Very good agreement was achieved when a diagnosis of dysplasia was based on the presence of both features (κ = 0.85).

CONCLUSIONS

There is high interobserver variability and a tendency to overdiagnose LGD in FGPs. Strict criteria requiring both surface atypia and abrupt transition for LGD in FGPs result in low interobserver variability.

The Chinese Society of Clinical Oncology (CSCO): Clinical guidelines for the diagnosis and treatment of gastric cancer, 2021

There exist differences in the epidemiological characteristics, clinicopathological features, tumor biological characteristics, treatment patterns, and drug selections between gastric cancer patients from the Eastern and Western countries. The Chinese Society of Clinical Oncology (CSCO) has organized a panel of senior experts specializing in all sub-specialties of gastric cancer to compile a clinical guideline for the diagnosis and treatment of gastric cancer since 2016 and renews it annually. Taking into account regional differences, giving full consideration to the accessibility of diagnosis and treatment resources, these experts have conducted expert consensus judgment on relevant evidence and made various grades of recommendations for the clinical diagnosis and treatment of gastric cancer to reflect the value of cancer treatment and meeting health economic indexes in China. The 2021 CSCO Clinical Practice Guidelines for Gastric Cancer covers the diagnosis, treatment, follow-up, and screening of gastric cancer. Based on the 2020 version of the CSCO Chinese Gastric Cancer guidelines, this updated guideline integrates the results of major clinical studies from China and overseas for the past year, focused on the inclusion of research data from the Chinese population for more personalized and clinically relevant recommendations. For the comprehensive treatment of non-metastatic gastric cancer, attentions were paid to neoadjuvant treatment. The value of perioperative chemotherapy is gradually becoming clearer and its recommendation level has been updated. For the comprehensive treatment of metastatic gastric cancer, recommendations for immunotherapy were included, and immune checkpoint inhibitors from third-line to the first-line of treatment for different patient groups with detailed notes are provided.

BRCA mutations and gastrointestinal cancers: When to expect the unexpected?

BRCA1/2 pathogenic variants are widely known as major risk factors mainly for breast and ovarian cancer, while their role in gastrointestinal (GI) malignancies such as colorectal cancer (CRC), gastric cancer and oesophageal cancer (OeC) is still not well established. The main objective of this review is to summarise the available evidence on this matter. The studies included in the review were selected from PubMed/GoogleScholar/ScienceDirect databases to identify published articles where BRCA1/2 pathogenic variants were assessed either as a risk factor or a prognostic/predictive factor in these malignancies. Our review suggests that BRCA1/2 might have a role as a risk factor for colorectal, gastric and OeC, albeit with differences among these diseases: In particular BRCA1 seems to be much more frequently mutated in CRC whereas BRCA2 appears to be much more closely associated with gastric and OeC. Early-onset cancer seems to be also associated with BRCA1/2 mutations and a few studies suggest a positive prognostic role of these mutations. The assessment of a potentially predictive role of these mutations is hampered by the fact that most patients with these diseases have been treated with platinum compounds, where it is expected that a higher probability of response should be seen. A few clinical trials focused on poly (ADP-ribose) polymerase inhibitors use in GI cancers are currently ongoing.

Deep neural network approaches for detecting gastric polyps in endoscopic images

Gastrointestinal endoscopy is the primary method used for the diagnosis and treatment of gastric polyps. The early detection and removal of polyps is vitally important in preventing cancer development. Many studies indicate that a high workload can contribute to misdiagnosing gastric polyps, even for experienced physicians. In this study, we aimed to establish a deep learning-based computer-aided diagnosis system for automatic gastric polyp detection. A private gastric polyp dataset was generated for this purpose consisting of 2195 endoscopic images and 3031 polyp labels. Retrospective gastrointestinal endoscopy data from the Karadeniz Technical University, Farabi Hospital, were used in the study. YOLOv4, CenterNet, EfficientNet, Cross Stage ResNext50-SPP, YOLOv3, YOLOv3-SPP, Single Shot Detection, and Faster Regional CNN deep learning models were implemented and assessed to determine the most efficient model for precancerous gastric polyp detection. The dataset was split 70% and 30% for training and testing all the implemented models. YOLOv4 was determined to be the most accurate model, with an 87.95% mean average precision. We also evaluated all the deep learning models using a public gastric polyp dataset as the test data. The results show that YOLOv4 has significant potential applicability in detecting gastric polyps and can be used effectively in gastrointestinal CAD systems. Gastric Polyp Detection Process using Deep Learning with Private Dataset.

Inherited Predisposition to Gastric Cancer

Approximately 10% of patients with gastric cancer show familial aggregation and up to 3% are related to an inherited cancer syndrome. There are multiple germline pathogenic variants and cancer syndromes associated with an increased risk of gastric cancer. Appropriate assessment of familial and genetic risk may allow a personalized approach to gastric cancer prevention through screening and risk-reducing surgeries. The ability to better identify carriers with pathogenic genetic variants associated with gastric cancer before a diagnosis of cancer requires effective genetic risk assessment and testing, followed by optimal screening and surveillance recommendations to further reduce the morbidity and mortality.

Japanese Society for Cancer of the Colon and Rectum (JSCCR) guidelines 2020 for the Clinical Practice of Hereditary Colorectal Cancer

Hereditary colorectal cancer (HCRC) accounts for < 5% of all colorectal cancer cases. Some of the unique characteristics commonly encountered in HCRC cases include early age of onset, synchronous/metachronous cancer occurrence, and multiple cancers in other organs. These characteristics necessitate different management approaches, including diagnosis, treatment or surveillance, from sporadic colorectal cancer management. There are two representative HCRC, named familial adenomatous polyposis and Lynch syndrome. Other than these two HCRC syndromes, related disorders have also been reported. Several guidelines for hereditary disorders have already been published worldwide. In Japan, the first guideline for HCRC was prepared by the Japanese Society for Cancer of the Colon and Rectum (JSCCR), published in 2012 and revised in 2016. This revised version of the guideline was immediately translated into English and published in 2017. Since then, several new findings and novel disease concepts related to HCRC have been discovered. The currently diagnosed HCRC rate in daily clinical practice is relatively low; however, this is predicted to increase in the era of cancer genomic medicine, with the advancement of cancer multi-gene panel testing or whole genome testing, among others. Under these circumstances, the JSCCR guidelines 2020 for HCRC were prepared by consensus among members of the JSCCR HCRC Guideline Committee, based on a careful review of the evidence retrieved from literature searches, and considering the medical health insurance system and actual clinical practice settings in Japan. Herein, we present the English version of the JSCCR guidelines 2020 for HCRC.

Gastritis, Gastric Polyps and Gastric Cancer

Gastric cancer is still an important disease causing many deaths worldwide, although there has been a marked reduction in prevalence during the last few decades. The decline in gastric cancer prevalence is due to a reduction in Helicobacter pylori infection which has occurred for at least 50 years. The most probable mechanism for the carcinogenic effect of H. pylori is hypergastrinemia since H. pylori infected individuals do not have increased risk of gastric cancer before the development of oxyntic atrophy. When atrophy has developed, the carcinogenic process continues independent of H. pylori. Autoimmune gastritis also induces oxyntic atrophy leading to marked hypergastrinemia and development of ECL cell neoplasia as well as adenocarcinoma. Similarly, long-term treatment with efficient inhibitors of acid secretion like the proton pump inhibitors (PPIs) predisposes to ECL cell neoplasia of a different degree of malignancy. Contrasting the colon where most cancers develop from polyps, most polyps in the stomach have a low malignant potential. Nevertheless, gastric polyps may also give rise to cancer and have some risk factors and mechanisms in common with gastric cancer. In this overview the most common gastric polyps, i.e., hyperplastic polyps, adenomatous polyps and fundic gland polyps will be discussed with respect to etiology and particularly use of PPIs and relation to gastric carcinogenesis.

Recent Advances in Digestive Tract Tumors: Updates From the 5th Edition of the World Health Organization "Blue Book"

CONTEXT.—

The World Health Organization Classification of Tumours: Digestive System Tumors, 5th edition, was published in 2019 and shows several impactful changes as compared with the 4th edition published in 2010. Changes include a revised nomenclature of serrated lesions and revamping the classification of neuroendocrine neoplasms. Appendiceal goblet cell adenocarcinoma is heavily revised, and intrahepatic cholangiocarcinoma is split into 2 subtypes. New subtypes of colorectal carcinoma and hepatocellular carcinoma are described. Precursor lesions are emphasized with their own entries, and both dysplastic and invasive lesions are generally recommended to be graded using a 2-tier system. Hematolymphoid tumors, mesenchymal tumors, and genetic tumor syndromes each have their own sections in the 5th edition. New hematolymphoid lesions include monomorphic epitheliotropic intestinal T-cell lymphoma; duodenal-type follicular lymphoma; intestinal T-cell lymphoma, not otherwise specified; and indolent T-cell lymphoproliferative disorder of the gastrointestinal tract. This paper will provide an in-depth look at the changes in the 5th edition as compared with the 4th edition.

OBJECTIVE.—

To provide a comprehensive, in-depth update on the World Health Organization classification of digestive tumors, including changes to nomenclature, updated diagnostic criteria, and newly described entities.

DATA SOURCES.—

The 5th edition of the World Health Organization Classification of Tumours: Digestive System Tumours, as well as the 4th edition.

CONCLUSIONS.—

The World Health Organization has made many key changes in its newest update on tumors of the digestive system. Pathologists should be aware of these changes and incorporate them into their practice as able or necessary.

Role of regulatory B cells in gastric cancer: Latest evidence and therapeutics strategies

Gastric cancer (GC) is the second most common cancer globally and kills about 700,000 people annually. Today's knowledge clearly shows a close and complicated relationship between the tumor microenvironment (TME) and the immune system. The immune system components can both stimulate tumor growth and inhibit tumor cells. However, numerous of these mechanisms are not yet fully understood. As an essential immune cell in humoral immunity, B lymphocytes can play a dual role during various pathologic states, including infections, autoimmune diseases, and cancer, depending on their phenotype and environmental signals. Inherently, B cells can inhibit tumor growth by producing antibodies as well as the presentation of tumor antigens. However, evidence suggests that a subset of these cells termed regulatory B cells (Bregs) with an inhibitory phenotype can suppress anti-tumor responses and support the tumor growth by producing anti-inflammatory cytokines and the expression of inhibitory molecules. Therefore, in this review, the role of Bregs in the microenvironment of GC and treatment strategies based on targeting this subset of B cells have been investigated.

Genetic Gastric Cancer Risk Syndromes

Purpose of review

Gastric cancer is a leading cause of cancer death in the world. Between 1% and 3% of cases are associated with specific genetic cancer risk syndromes. The purpose of this article is to review the latest insights, as well as gaps in knowledge, regarding some of the most common hereditary gastric cancer syndromes: hereditary diffuse gastric cancer (HDGC), gastric adenocarcinoma and proximal polyposis of the stomach (GAPPS), Lynch syndrome, the adenomatous polyposis syndromes, and the hamartomatous polyposis syndromes.

Recent findings

Patients carrying pathogenic variants in CDH1, but not meeting clinical criteria for HDGC, are increasingly being identified thanks to multigene panel testing; their absence from previous analyses overestimated gastric cancer penetrance. GAPPS is a recently described hereditary gastric cancer syndrome associated with specific point mutations in the promoter 1B region of the APC gene.

Summary

Risk of gastric cancer is highest among carriers of pathogenic variants in CDH1, with cumulative incidences approximately 40% and 30% for men and women, respectively. Mutations associated with Lynch syndrome and adenomatous polyposis syndromes confer greatest risk for gastric cancer in East Asian populations. Risk of gastric cancer in GAPPS and hamartomatous polyposis syndromes is difficult to estimate due to their rarity, but mutation status likely determines risk. Future research is needed to more precisely define risk of gastric cancer in these syndromes, so strategies for screening and prophylactic gastrectomy can be optimized.

Disease spectrum of gastric cancer susceptibility genes

Pathogenic variants in germline cancer susceptibility genes can increase the risk of a large number of diseases. Our study aims to assess the disease spectrum of gastric cancer susceptibility genes and to develop a comprehensive resource of gene-disease associations for clinicians. Twenty-seven potential germline gastric cancer susceptibility genes were identified from three review articles and from six commonly used genetic information resources. The diseases associated with each gene were evaluated via a semi-structured review of six genetic resources and an additional literature review using a natural language processing (NLP)-based procedure. Out of 27 candidate genes, 13 were identified as gastric cancer susceptibility genes (APC, ATM, BMPR1A, CDH1, CHEK2, EPCAM, MLH1, MSH2, MSH6, MUTYH-Biallelic, PALB2, SMAD4, and STK11). A total of 145 gene-disease associations (with 45 unique diseases) were found to be associated with these 13 genes. Other gastrointestinal cancers were prominent among identified associations, with 11 of 13 gastric cancer susceptibility genes also associated with colorectal cancer, eight genes associated with pancreatic cancer, and seven genes associated with small intestine cancer. Gastric cancer susceptibility genes are frequently associated with other diseases as well as gastric cancer, with potential implications for how carriers of these genes are screened and managed. Unfortunately, commonly used genetic resources provide heterogeneous information with regard to these genes and their associated diseases, highlighting the importance of developing guides for clinicians that integrate data across available resources and the medical literature.

Beyond the Guidelines: The Grey Zones of the Management of Gastric Cancer. Consensus Statements from the Gastric Cancer Italian Network (GAIN)

BACKGROUND

Management of gastric and gastroesophageal junction (GEJ) adenocarcinoma remains challenging, because of the heterogeneity in tumor biology within the upper gastrointestinal tract. Daily clinical practice is full of grey areas regarding the complexity of diagnostic, staging, and therapeutic procedures. The aim of this paper is to provide a guide for clinicians facing challenging situations in routine practice, taking a multidisciplinary consensus approach based on available literature.

METHODS

The GAIN (GAstric cancer Italian Network) group was established with the aims of reviewing literature evidence, discussing key issues in prevention, diagnosis, and management of gastric and GEJ adenocarcinoma, and offering a summary of statements. A Delphi consensus method was used to obtain opinions from the expert panel of specialists.

RESULTS

Forty-nine clinical questions were identified in six areas of interest: role of multidisciplinary team; risk factors; diagnosis; management of early gastric cancer and multimodal approach to localized gastric cancer; treatment of elderly patients with locally advanced resectable disease; and treatment of locally advanced and metastatic cancer.

CONCLUSIONS

The statements presented may guide clinicians in practical management of this disease.

Helicobacter pylori-negative Gastric Cancer

<i>Helicobacter pylori (H. pylori)</i>-negative gastric cancer is diagnosed when gastric malignancies are found in patients in <i>H. pylori</i>-naïve stomachs. There are four types of noncardiac <i>H. pylori</i>-negative gastric cancers. The signet ring cell-type poorly cohesive carcinoma is most common, followed by the chief cell-predominant type gastric adenocarcinoma of the fundic gland. Extremely well-differentiated adenocarcinoma of the corpus and well-differentiated pyloric gland cancers are rare outside Japan because of country-specific differences in diagnostic criteria. In endemic areas of <i>H. pylori</i> infection, strict criteria are required for diagnosing an <i>H. pylori</i>-naïve stomach. Both invasive and noninvasive <i>H. pylori</i> tests should show negative results in a subject without a history of <i>H. pylori</i> infection. Furthermore, the serum pepsinogen (PG) assay and endoscopic findings of the background gastric mucosa are required to discriminate subjects with past infections owing to spontaneous regression or unintended eradication of <i>H. pylori</i>. There should be no gastric corpus atrophy (PG I ≤70 ng/mL and PG I/II ≤3.0). Gastroscopy should reveal a regular arrangement of collecting venules without gastric xanthoma, metaplastic gastritis, or advanced atrophy over the angle. On biopsy, there should be no gastric atrophy, intestinal metaplasia, neutrophils, or <i>H. pylori</i> infiltration, and only a mild degree of mononuclear cell infiltration is permitted. The types and characteristics of noncardiac <i>H. pylori</i>-negative gastric cancers are summarized in this review, along with current diagnostic challenges found in Korea.

Gastric adenocarcinoma and proximal polyposis of the stomach (GAPPS) - A Helicobacter-opposite point

Gastric adenocarcinoma and proximal polyposis of the stomach (GAPPS) is a rare familial gastric cancer syndrome with an autosomal dominant pattern of inheritance. It is characterised by fundic gland polyposis of the gastric body and is associated with a significant risk of gastric adenocarcinoma. Unlike sporadic gastric cancer, Helicobacter pylori is usually absent in patients with GAPPS. This opposite-point finding has so far not been fully clarified. Prophylactic total gastrectomy is indicated in all cases of GAPPS with fundic gland polyposis and the presence of any dysplasia. If no dysplasia is found at histology, prophylactic gastrectomy is suggested at between 30 and 35 years of age, or at five years earlier than the age at which the youngest family member developed gastric cancer. Different phenotypes of GAPPS demand an individual approach to particular family members.

Non-conventional dysplasias of the tubular gut: a review and illustration of their histomorphological spectrum

The increasing use of gastrointestinal endoscopic procedures has led to the recognition by histopathologists of non-conventional (or special-type) dysplasias of the gastrointestinal tract. These lesions can be recognised in association with prevalent underlying gastrointestinal conditions, such as Barrett oesophagus, chronic atrophic gastritis, and inflammatory bowel disease. The diagnosis of these special types can be challenging, and their biological behaviours are not fully characterised. The aim of this review is to provide a global view of non-conventional dysplastic lesions observed in the various segments of the tubular gastrointestinal tract and describe their salient features. Furthermore, as the clinical implications of these various subtypes have not been broadly tested in practice and are not represented in most management guidelines, we offer guidance on the best management practices for these lesions.

Recent advances in the pathology of heritable gastric cancer syndromes

Despite the relative rarity of hereditary gastric cancer syndromes, the prompt recognition of their specific clinical features and histopathological characteristics is pivotal in offering patients the most appropriate treatment. In this article, we address the three major inherited syndromes that primarily affect the stomach: hereditary diffuse gastric cancer (HDGC), caused by germline variants in CDH1 and CTNNA1; gastric adenocarcinoma and proximal polyposis of the stomach, caused by germline mutations in promoter 1B of APC; and familial intestinal gastric cancer, which has a poorly defined genetic cause. The main focus will be on HDGC, in light of the recent publication of updated clinical practice guidelines and emerging concepts regarding HDGC histopathology. In particular, we describe the broad morphological spectrum of HDGC lesions, stressing the importance of recognising indolent and aggressive phenotypes. Moreover, we discuss the increased risk of gastric (pre)malignancies developing in patients with other well-defined hereditary cancer syndromes, such as familial adenomatous polyposis, Lynch syndrome, Peutz-Jeghers syndrome, juvenile polyposis, Li-Fraumeni syndrome, and hereditary breast and ovarian cancer syndrome.

Novel Pathogenic Germline Variant of the Adenomatous Polyposis Coli (APC) Gene, p.S2627Gfs*12 Identified in a Mild Phenotype of APC-Associated Polyposis: A Case Report

Patient: Male, 80-year-old

Final Diagnosis: Attenuated APC-associated polyposis

Symptoms: Colon polyps • renal carcinoma

Medication: —

Clinical Procedure: —

Specialty: Genetics

Targeted next-generation sequencing as a diagnostic tool in gastrointestinal system cancer/polyposis patients

Background:

Recent advances in next-generation sequencing (NGS) technology have enabled multigene testing and changed the diagnostic approach to hereditary gastrointestinal cancer/polyposis syndromes. The aim of this study was to analyze different cancer predisposition genes in hereditary/sporadic gastrointestinal cancer/polyposis.

Methods:

Cancer predisposition genes were analyzed with an Illumina MiSeq NGS system in 80 patients with gastrointestinal cancer/polyposis who were examined between the years 2016 and 2019. Deletion/duplication analysis of MLH1, MSH2, and EPCAM genes was performed by using the multiplex ligation-dependent probe amplification method.

Results:

Germline testing of hereditary cancer-related genes was performed in 80 patients with gastrointestinal cancer/polyposis. A total of 30 variants in 30 cases (37.5%) were assessed as pathogenic/likely pathogenic. A total of 19 heterozygous variants were assessed as variants of uncertain clinical significance in 17 cases (21.25%) and 18 (22.5%) novel variations (9 pathogenic/likely pathogenic, 9 variants of uncertain significance) were determined. In 4 (5%) cases, multiplex ligation-dependent probe amplification detected deletions in MLH1, MSH2, and EPCAM genes.

Conclusion:

The accumulation of analyses with multigene testing will increase the available data for cancer predisposition genes in hereditary gastrointestinal cancer/polyposis. Educational campaigns for prevention, efficient screening programs, and more personalized care based on the profile of individual patients are necessary.

Two Asian families with gastric adenocarcinoma and proximal polyposis of the stomach successfully treated via laparoscopic total gastrectomy

Family 1: a 39-year-old woman and her sister were admitted to our hospital for fundic gland polyps (FGPs). Their mother died of gastric cancer with FGPs. We performed repeated biopsies at close intervals, suspecting gastric adenocarcinoma and proximal polyposis of the stomach (GAPPS). After a 1-year follow-up, the sisters were diagnosed with gastric cancer with FGP. We performed laparoscopic total gastrectomies with D1+lymph node dissection. Promoter 1B (exon 1B) of the APC gene (chr5: 112,043,224 T>C) contained a point mutation. The sisters were subsequently diagnosed with GAPPS as per the mutational analysis. Family 2 (unrelated to Family 1): a-24-year-old woman was referred for epigastralgia. EGD revealed FGPs localized in the proximal stomach. Pathological biopsy results showed severe dysplasia and adenocarcinoma in situ. Her father was simultaneously diagnosed with FGPs with GC localized in the proximal stomach. We performed laparoscopic total gastrectomies with D1+lymph node dissection. They had the same gene mutation as the family 1. Here, we report two Asian families with GAPPS successfully treated via laparoscopic total gastrectomy.

Diffuse gastric cancer: histologic, molecular, and genetic basis of disease

Diffuse gastric cancer (DGC) is a distinct histopathologic and molecular disease, characterized by mutations in CDH1, RHOA, and others. In addition, DGC is associated with familial syndromes, including hereditary DGC and germline mutation in CDH1. Clinically, this subtype of gastric adenocarcinoma is associated with a poor prognosis and possible resistance to available systemic therapies. An understanding of the genetic and molecular underpinnings of DGC may help inform of its clinical behavior and aid in screening, diagnosis, and response to treatment. In this review, we will review the current histologic, molecular, and genetic landscape of DGC and its relevance to clinical practice.

Two independent families with strongly suspected hereditary diffuse gastric cancer based on the probands' endoscopic findings

Hereditary diffuse gastric cancer (HDGC) is the most famous of hereditary gastric cancer syndromes with an autosomal dominant inheritance pattern, and its diagnosis can be made by identifying a pathogenic germline variant in CDH1. We report two independent families that were strongly suspected of having HDGC based on endoscopic findings (multiple tiny, pale areas) obtained in the probands; the probands were pathologically diagnosed as having signet ring cell carcinoma (SRCC) and were genetically confirmed to have a pathogenic CDH1 germline variant. Although the updated International Gastric Cancer Linkage Consortium (IGCLC)'s clinical guidelines for HDGC (2015) state that screening/surveillance endoscopy should be performed (Cambridge protocol), the endoscopic findings obtained in the two presently reported families suggest that pale areas should be suspected as indicating the presence of SRCCs, and biopsies should be performed in addition to obtaining a precise family history in cases suspected of having HDGC.

Precancerous lesions of the stomach, gastric cancer and hereditary gastric cancer syndromes

Gastric cancer accounts for about 6% of cancers worldwide, being the fifth most frequently diagnosed malignancy and the third leading cause of cancer related death. Gastric carcinogenesis is a multistep and multifactorial process and is the result of the complex interplay between genetic susceptibility and environmental factors. The identification of predisposing conditions and of precancerous lesions is the basis for screening programs and early stage treatment. Furthermore, although most gastric cancers are sporadic, familial clustering is observed in up to 10% of patients. Among them, hereditary cases, related to known cancer susceptibility syndromes and/or genetic causes are thought to account for 1-3% of all gastric cancers. The pathology report of gastric resections specimens therefore requires a standardized approach as well as in depth knowledge of prognostic and treatment associated factors.

Gastric cancer

Gastric cancer is the fifth most common cancer and the third most common cause of cancer death globally. Risk factors for the condition include Helicobacter pylori infection, age, high salt intake, and diets low in fruit and vegetables. Gastric cancer is diagnosed histologically after endoscopic biopsy and staged using CT, endoscopic ultrasound, PET, and laparoscopy. It is a molecularly and phenotypically highly heterogeneous disease. The main treatment for early gastric cancer is endoscopic resection. Non-early operable gastric cancer is treated with surgery, which should include D2 lymphadenectomy (including lymph node stations in the perigastric mesentery and along the celiac arterial branches). Perioperative or adjuvant chemotherapy improves survival in patients with stage 1B or higher cancers. Advanced gastric cancer is treated with sequential lines of chemotherapy, starting with a platinum and fluoropyrimidine doublet in the first line; median survival is less than 1 year. Targeted therapies licensed to treat gastric cancer include trastuzumab (HER2-positive patients first line), ramucirumab (anti-angiogenic second line), and nivolumab or pembrolizumab (anti-PD-1 third line).

De novo adolescent gastric carcinoma: a first case report in Saskatchewan, Canada

Adolescent gastric cancers are extremely rare with a reported incidence of 0.05-0.10% in North America. We present a de novo case of gastric carcinoma in a 17-year-old teenager with no concomitant family history or risk factors. His main clinical presentation included anaemia and melaena stools. Despite an extensive clinical workup that included a diagnostic laparoscopy, the tumour was deemed surgically irresectable, and he was started on a palliative chemotherapy protocol at the local paediatric oncology centre. He demised 7 months later. This is the first recorded case of an adolescent gastric cancer in Saskatchewan, Canada. This case highlights the need for an international tumour registry to document and investigate rare adolescent gastric malignancies and thereby potentiate a possible cure through the pooling of limited resources.

Gastric cancer: epidemiology, biology, and prevention: a mini review

Gastric cancer is one of the most common causes of cancer-related mortality worldwide. The objective of this article is to review the epidemiology and biology of gastric cancer risk. This literature review explores the biological, clinical, and environmental factors that influence the rates of this disease and discuss the different intervention methods that may not only increase the awareness of gastric cancer but also increase screening in efforts to reduce the risk of gastric cancer. Helicobacter pylori infection is the primary risk factor for gastric cancer. Additional risk factors include geographical location, age, sex, smoking, socioeconomic status, dietary intake, and genetics. Primary and secondary prevention strategies such as dietary modifications and screenings are important measures for reducing the risk of gastric cancer. Interventions, such as H. pylori eradication through chemoprevention trials, have shown some potential as a preventative strategy. Although knowledge about gastric cancer risk has greatly increased, future research is warranted on the differentiation of gastric cancer epidemiology by subsite and exploring the interactions between H. pylori infection, genetics, and environmental factors. Better understanding of these relationships can help researchers determine the most effective intervention strategies for reducing the risk of this disease.

Gastric Epithelial Polyps: When to Ponder, When to Panic

This review provides an overview of different types of gastric epithelial polyps. The polyps are classified based on their cell or epithelial compartment of origin. Some of these polyps can be considered reactive or nonneoplastic, whereas others are neoplastic in origin, are sometimes associated with a hereditary polyposis/cancer syndrome, and may have malignant potential. The aim of this review is to provide a pragmatic overview for the practicing pathologist about how to correctly diagnose and deal with gastric epithelial polyps and when (not) to ponder, and when (not) to panic.

The clinicopathological and molecular features of sporadic gastric foveolar type neoplasia

Gastric intraepithelial foveolar type neoplasia (IEFN) is not well defined. In addition, atrophic mucosa (AM) is an important issue to consider when evaluating gastric tumorigenesis. Here, we assessed the clinicopathological characteristics and molecular alterations contributing to the development of IEFN compared with intestinal type neoplasia. We examined the clinicopathological and molecular features of 42 cases of IEFN with low-grade dysplasia (LGD) and those of 77 cases of intraepithelial intestinal type neoplasia (IEIN) with LGD. The clinicopathological and molecular features examined included the AM status, mucin phenotype expression, CDX2 expression, p53 overexpression, β-catenin intranuclear accumulation, microsatellite instability (MSI), DNA methylation status (low methylation epigenotype [LME], intermediate ME, or high ME), allelic imbalances (AIs), and APC promoter 1B mutations. There were no differences in the frequencies of AM and rates of CDX2 expression between IEFN and IEIN cases. Although no differences in the frequencies of p53 overexpression and MSI were observed between the two histological types, intranuclear expression of β-catenin was significantly higher in IEIN than in IEFN. In addition, although the rate of LME was significantly higher in IEFN cases than in IEIN cases, IEFN was characterized by AIs at multiple foci. Finally, mutation of the APC promoter 1B, which is a characteristic of gastric adenocarcinoma and proximal polyposis of the stomach (potentially resembling IEFN), was detected in only one IEFN case. These findings suggested that IEFN may be an independent entity in terms of molecular alterations including the presence of multiple AIs and LME.

Increased risk for uterine cancer among first-degree relatives to Swedish gastric cancer patients

Purpose

In order to further understand genetically predisposing factors of gastric cancer, a retrospective study on 107 patients with gastric cancer was conducted. The family history of cancer cases was registered, in search of associations between gastric cancer and other cancer types.

Materials and methods

Within Stockholm County in Sweden, all patients previously diagnosed with gastric cancer and still alive were invited to participate in the study. Patients were asked to complete a questionnaire about their gastric cancer diagnosis and if any cancers had occurred in their family. A blood sample for DNA extraction was collected. The proportions of different cancer types in the relatives of the patients were compared to the general Swedish population in 1970 and 2010.

Results

Among first- and second-degree relatives to the index patients with gastric cancer, the frequency of uterine cancer as well as gastric cancer was significantly overrepresented compared to the general population in Sweden. The frequency of breast cancer was significantly lower.

Conclusions

There seems to be an increased risk of both gastric cancer and uterine cancer in the families of gastric cancer survivors, indicating a possible hereditary connection between these two cancer types.

A case of gastric adenocarcinoma considered to originate from a sporadic fundic gland polyp in a Helicobacter pylori-uninfected stomach

We encountered a rare case of gastric adenocarcinoma considered to arise from a sporadic fundic gland polyp (FGP). A woman in her 70 s, who had been prescribed a proton pump inhibitor for 5 years, was referred to our institution for further investigation and treatment of a gastric lesion. White light endoscopy showed numerous isochromatic FGPs in the greater curvature of the gastric body and a 15-mm reddish polypoid lesion with uneven surface characteristics. Magnifying endoscopy with narrow band imaging revealed an irregular granular microsurface structure with irregular microvessels, which is suggestive of cancer. The absence of atrophic changes in the entire gastric mucosa was confirmed endoscopically and histologically, and multiple Helicobacter pylori (HP) tests were negative. An en bloc resection was performed by polypectomy. The specimen showed adenocarcinoma that was thought to arise from an FGP. The lesion consisted of cystically dilated fundic glands in the basal part and neoplastic cells with nuclear atypia and high nuclear-cytoplasmic ratio in the foveolar part; on the basis of these findings, noninvasive adenocarcinoma was diagnosed. Although both adenocarcinoma in an HP-uninfected stomach and epithelial high-grade dysplasia in a sporadic FGP are extremely rare, this possibility should be considered when performing esophagogastroduodenoscopy.

Les cancers colorectaux héréditaires vus par le pathologiste

The pathologist's role in the management of hereditary colorectal cancer is important. The pathologist may suspect a familial cancer when particular morphological and/or clinical criteria are present or give a response to a clinical request in the context of a possible hereditary cancer. In this setting, the pathologist's conclusions have necessarily to be integrated to a precise environment, and if needed, followed by an oncogenetic consultation and a germline mutation research. The aim of this article is to present the main aspects of hereditary colon cancers that a pathologist may see, but also to highlight the histopathological characteristics and the place of the pathologist in the management of these different entities.

[Hereditary gastric cancer: Challenges for the pathologist in 2020]

Gastric cancer is the third most common cancer worldwide. The majority of gastric cancers are sporadic but familial clustering is seen in more than 10% of cases. This manuscript is divided into two parts. The first part is dedicated to the non-syndromic hereditary gastric cancer, particularly the hereditary diffuse gastric cancer (HDGC) and other gastric polyposes including the recently described GAPPS (Gastric adenocarcinoma and proximal polyposis of the stomach). The second part concerns the syndromic gastric cancer, namely the HNPCC syndrome (Hereditary Non Polyposis Colorectal Cancer) occurring as part of a genetic predisposition syndrome to cancer. Recent advances in oncogenetics and next generation sequencing technology have enabled the identification of new entities. This enhancement in knowledge regarding inherited syndromes predisposing to gastric cancer has consequently improved the management of patients and their families. In this context, pathologists play a major role in identifying particular morphologic entities prompting genetic investigation. The aim of this manuscript is to provide an update on the current knowledge about hereditary gastric cancer.

Redefinition of familial intestinal gastric cancer: clinical and genetic perspectives

BACKGROUND

Familial intestinal gastric cancer (FIGC) remains genetically unexplained and without testing/clinical criteria. Herein, we characterised the age of onset and disease spectrum of 50 FIGC families and searched for genetic causes potentially underlying a monogenic or an oligogenic/polygenic inheritance pattern.

METHODS

Normal and tumour DNA from 50 FIGC probands were sequenced using Illumina custom panels on MiSeq, and their respective germline and somatic landscapes were compared with corresponding landscapes from sporadic intestinal gastric cancer (SIGC) and hereditary diffuse gastric cancer cohorts.

RESULTS

The most prevalent phenotype in FIGC families was gastric cancer, detected in 138 of 208 patients (50 intestinal gastric cancer probands and 88 unknown gastric cancer histology relatives), followed by colorectal and breast cancers. After excluding benign and intronic variants lacking impact in splicing, 12 rare high-quality variants were found exclusively in 11 FIGC probands. Only two probands carried potentially deleterious variants, but lacked somatic second-hits, weakly supporting the monogenic hypothesis for FIGC. However, FIGC probands developed gastric cancer at least 10 years earlier and carried more TP53 germline common variants than SIGC (p=4.5E-03); FIGC and SIGC could be distinguished by specific germline and somatic variant profiles; there was an excess of FIGC tumours presenting microsatellite instability (38%); and FIGC tumours displayed significantly more somatic common variants than SIGC tumours (p=4.2E-06).

CONCLUSION

This study proposed the first data-driven testing criteria for FIGC families, and supported FIGC as a genetically determined, likely polygenic, gastric cancer-predisposing disease, with earlier onset and distinct from patients with SIGC at the germline and somatic levels.

Novel Variants and Copy Number Variation in CDH1 Gene in Iranian Patients with Sporadic Diffuse Gastric Cancer

INTRODUCTION

The aim of this study was to survey the nucleotide changes and copy number variations (CNV) in the CDH1 gene in Iranian patients with sporadic diffuse gastric cancer (SDGC).

MATERIALS AND METHODS

In this study, 28 patients were examined who upon gastrectomy had been diagnosed with SDGC according to the familial history and histopathological criteria which was confirmed by the pathologist. DNA extraction was performed from formalin-fixed paraffin-embedded tissues using a phenol-chloroform method following xylene deparaffinization. Determination of DNA sequence by Sanger was performed using PCR amplification of 16 exons and boundaries of intron/exon of CDH1 gene. Multiplex ligation-dependent probe amplification (MLPA) was performed on patients with pathogenic disorders in the sequence.

RESULTS

In total, patients included 20 males and 8 females. Of all patients, 12 patients were under 45 years old (early onset gastric cancer, EODC) and 16 patients were older. The tumor was diagnosed in the early TNM stage (I, II) in six patients and in late stages (III, IV) in 19 cases. Altogether, 16 variants (three exonic with one new variant and 13 intronic with nine new variants) were found in DNA sequencing of the CDH1 gene in five samples. Also, using MLPA, a new duplication in exon 9 and one deletion in exon 2 were detected in two other patients. Altogether, CDH1 variants were identified in seven out of 28 patients (25%).

CONCLUSION

Our study revealed several novel somatic variants in the CDH1 gene in Iranian patients with sporadic diffuse GC. Our data supports the hypothesis that mutations in CDH1 gene, and particularly the mutations we describe, should be considered, even in sporadic cases of gastric cancer. The presence of these mutations in patients raises important issues regarding genetic counseling and diagnostic test in DGC patients.

Hereditary gastric cancer: what's new? Update 2013-2018

Around 10-20% of gastric cancer patients have relatives with a diagnosis of GC and in 1-3% of patients a genetic cause can be confirmed. Histopathologically, GC is classified into intestinal-type, with glandular growth, and diffuse-type with poorly cohesive growth pattern often with signet ring cells. Familial or hereditary GC is classified into hereditary diffuse GC (HDGC), familial intestinal GC (FIGC) and polyposis forms. This review focuses on recent research findings and new concepts of hereditary GC.

Hereditary Polyposis Syndromes

PURPOSE OF REVIEW

Colorectal cancer (CRC) is the third most common cancer in the USA and inherited cancer syndromes are responsible for approximately 3-5% of all CRCs. Genetic testing costs have plummeted in recent years; however, awareness and referral of high-risk patients for testing is still very low. We review the salient clinical features, genetics, and management of well-defined gastrointestinal (GI) hereditary polyposis syndromes including familial adenomatous polyposis, MUTYH-associated polyposis, and the hamartomatous polyposis syndromes.

RECENT FINDINGS

Comprehensive endoscopic surveillance has the potential to prevent the development of GI cancer and to identify early-stage cancer; newer developments like high-definition endoscopes, chromoendoscopy, and the use of cap-assisted endoscopy have shown promise for enhanced lesion detection rates. Several chemoprevention trials have yielded promising results but safety and efficacy data for long-term use is still awaited. Several new polyposis genes have also been identified in the recent years. Multiple societies have recently published updated surveillance guidelines to aid clinicians in the detection and management of patients with hereditary GI polyposis syndromes. Although these syndromes are rare, it is crucial for the clinicians to recognize these in a timely manner, for the appropriate management plans for both the patient and their at risk family members.

Multigene Panel Testing Increases the Number of Loci Associated with Gastric Cancer Predisposition

The main gene involved in gastric cancer (GC) predisposition is CDH1, the pathogenic variants of which are associated with diffuse-type gastric cancer (DGC) and lobular breast cancer (LBC). CDH1 only explains a fraction (10–50%) of patients suspected of DGC/LBC genetic predisposition. To identify novel susceptibility genes, thus improving the management of families at risk, we performed a multigene panel testing on selected patients. We searched for germline pathogenic variants in 94 cancer-related genes in 96 GC or LBC Italian patients with early-onset and/or family history of GC. We found CDH1 pathogenic variants in 10.4% of patients. In 11.5% of cases, we identified loss-of-function variants in BRCA1, BRCA2, PALB2, and ATM breast/ovarian cancer susceptibility genes, as well as in MSH2, PMS2, BMPR1A, PRF1, and BLM genes. In 78.1% of patients, we did not find any variants with clear-cut clinical significance; however, 37.3% of these cases harbored rare missense variants predicted to be damaging by bioinformatics tools. Multigene panel testing decreased the number of patients that would have otherwise remained genetically unexplained. Besides CDH1, our results demonstrated that GC pathogenic variants are distributed across a number of susceptibility genes and reinforced the emerging link between gastric and breast cancer predisposition.