Updated European guidelines for clinical management of familial adenomatous polyposis (FAP), MUTYH-associated polyposis (MAP), gastric adenocarcinoma, proximal polyposis of the stomach (GAPPS) and other rare adenomatous polyposis syndromes: a joint EHTG-ESCP revision.

BACKGROUND: Hereditary adenomatous polyposis syndromes, including familial adenomatous polyposis and other rare adenomatous polyposis syndromes, increase the lifetime risk of colorectal and other cancers. METHODS: A team of 38 experts convened to update the 2008 European recommendations for the clinical management of patients with adenomatous polyposis syndromes. Additionally, other rare monogenic adenomatous polyposis syndromes were reviewed and added. Eighty-nine clinically relevant questions were answered after a systematic review of the existing literature with grading of the evidence according to Grading of Recommendations, Assessment, Development, and Evaluation methodology. Two levels of consensus were identified: consensus threshold (≥67% of voting guideline committee members voting either 'Strongly agree' or 'Agree' during the Delphi rounds) and high threshold (consensus ≥ 80%). RESULTS: One hundred and forty statements reached a high level of consensus concerning the management of hereditary adenomatous polyposis syndromes. CONCLUSION: These updated guidelines provide current, comprehensive, and evidence-based practical recommendations for the management of surveillance and treatment of familial adenomatous polyposis patients, encompassing additionally MUTYH-associated polyposis, gastric adenocarcinoma and proximal polyposis of the stomach and other recently identified polyposis syndromes based on pathogenic variants in other genes than APC or MUTYH. Due to the rarity of these diseases, patients should be managed at specialized centres.

Solving Missing Heritability in Patients With Familial Adenomatous Polyposis With DNA-RNA Paired Testing.

PURPOSE: Patients with germline pathogenic variants (PVs) in APC develop tens (attenuated familial adenomatous polyposis [AFAP]) to innumerable (classic FAP) adenomatous polyps in their colon and are at significantly increased lifetime risk of colorectal cancer. Up to 10% of FAP and up to 50% of patients with AFAP who have undergone DNA-only multigene panel testing (MGPT) do not have an identified PV in APC. We seek to demonstrate how the addition of RNA sequencing run concurrently with DNA can improve detection of germline PVs in individuals with a clinical presentation of AFAP/FAP. METHODS: We performed a retrospective query of individuals tested with paired DNA-RNA MGPT from 2021 to 2022 at a single laboratory and included those with a novel APC PV located in intronic regions infrequently covered by MGPT, a personal history of polyposis, and family medical history provided. All clinical data were deidentified in this institutional review board-exempt study. RESULTS: Three novel APC variants were identified in six families and were shown to cause aberrant splicing because of the creation of a deep intronic cryptic splice site that leads to an RNA transcript subject nonsense-mediated decay. Several carriers had previously undergone DNA-only genetic testing and had received a negative result. CONCLUSION: Here, we describe how paired DNA-RNA MGPT can be used to solve missing heritability in FAP families, which can have important implications in family planning and treatment decisions for patients and their families.

Diffuse familial adenomatous intestinal polyposis in childhood: current state of the problem and case report.

OBJECTIVE: Aim: To explore the prevalence, clinical characteristics, and diagnostic aspects of diffuse familial adenomatous polyposis in childhood. This objective is accomplished through an extensive review of recent literature, and the presentation of case report from our clinical practice. PATIENTS AND METHODS: Materials and Methods: We analyzed 75 scientific papers, the findings of which have been documented in the PubMed database. Our search criteria included keywords such as ≪diffuse familial adenomatous intestinal polyposis,≫ ≪children,≫ and ≪diagnosis.≫ Then we conducted a second-stage analysis that involved a detailed review of a practical case - the medical records of inpatient Kh.V. who had been diagnosed with familial adenomatous polyposis. CONCLUSION: Conclusions: The analysis of the literature data is consistent with the findings from our clinical observations of familial adenomatous polyposis in a patient with complicated family anamnesis. It is worth noting that clinical features do not significantly differ across various types of polyposis. In cases of suspected familial adenomatous polyposis in adolescents, genetic testing is crucial.

Microenvironmental changes in familial adenomatous polyposis during colorectal cancer carcinogenesis.

Familial adenomatous polyposis (FAP) is a heritable disease that increases the risk of colorectal cancer (CRC) development because of heterozygous mutations in APC. Little is known about the microenvironment of FAP. Here, single-cell RNA sequencing was performed on matched normal tissues, adenomas, and carcinomas from four patients with FAP. We analyzed the transcriptomes of 56,225 unsorted single cells, revealing the heterogeneity of each cell type, and compared gene expression among tissues. Then we compared the gene expression with that of sporadic CRC. Furthermore, we analyzed specimens of 26 FAP patients and 40 sporadic CRC patients by immunohistochemistry. Immunosuppressiveness of myeloid cells, fibroblasts, and regulatory T cells was upregulated even in the early stages of carcinogenesis. CD8+ T cells became exhausted only in carcinoma, although the cytotoxicity of CD8+ T cells was gradually increased according to the carcinogenic step. When compared with those in the sporadic CRC microenvironment, the composition and function of each cell type in the FAP-derived CRC microenvironment had differences. Our findings indicate that an immunosuppressive microenvironment is constructed from a precancerous stage in FAP.

[Interpretation on genetic tumour syndromes in the 5th WHO classification of paediatric tumours: part â ¡].

WHO firstly published the classification of paediatric tumours, in which genetic tumour syndromes were introduced as a separate chapter, covering the clinicopathological features, molecular genetic alterations, and diagnostic criteria of various tumor susceptibility syndromes common in children. This article briefly introduces and interprets 5 hotspot genetic tumour syndromes (neurofibromatosis type 1, naevoid basal cell carcinoma syndrome, von Hippel-Lindau syndrome, familial adenomatous polyposis and xeroderma pigmentosum) based on relevant literature, in order to bring new perspectives and insights to pathologists and clinicians.

Re-evaluating the genotypes of patients with adenomatous polyposis of unknown etiology: a nationwide study.

In the Danish Polyposis Register, patients with over 100 cumulative colorectal adenomas of unknown genetic etiology, named in this study colorectal polyposis (CP), is registered and treated as familial adenomatous polyposis (FAP). In this study, we performed genetic analyses, including whole genome sequencing (WGS), of all Danish patients registered with CP and estimated the detection rate of pathogenic variants (PV). We identified 231 families in the Polyposis Register, 31 of which had CP. A polyposis-associated gene panel was performed and, if negative, patients were offered WGS and screening for mosaicism in blood and/or adenomas. Next-generation sequencing (NGS) was carried out for 27 of the families (four declined). PVs were detected in 11 families, and WGS revealed three additional structural variants in APC. Mosaicism of a PV in APC was detected in two families. As the variant detection rate of eligible families was 60%, 93% of families in the register now have a known genetic etiology.

Pachydysostosis of the fibula in a case of familial adenomatous polyposis.

BACKGROUND: Familial Adenomatous Polyposis (FAP) is a colorectal cancer (CRC) predisposition syndrome caused by germline APC mutations and characterised by an increased risk of CRC and colonic polyps and, in certain forms, of specific prominent extraintestinal manifestations, namely osteomas, soft tissue tumours and dental anomalies. Pachydysostosis of the fibula is a rare clinical entity defined by unilateral bowing of the distal portion of the fibula and elongation of the entire bone, without affectation of the tibia. CLINICAL REPORT: We report a 17-year-old male, who presented with a non-progressive bowing of the right leg detected at 18 months of age caused by a fibula malformation (later characterized as pachydysostosis) and a large exophytic osteoma of the left radius, noticed at the age of 15 years, without gastrointestinal symptoms. There was no relevant family history. Detailed characterisation revealed multiple osteomas, skin lesions and dental abnormalities, raising the hypothesis of FAP. This diagnosis was confirmed by genetic testing [c.4406_4409dup p.(Ala1471Serfs*17) de novo mutation in the APC gene] and endoscopic investigation (multiple adenomas throughout the colon, ileum and stomach). DISCUSSION: This case report draws attention to the phenotypic spectrum of skeletal manifestations of FAP: this patient has a congenital fibula malformation, not previously associated with this syndrome, but which is likely to have been its first manifestation in this patient. This clinical case also illustrates the challenges in the early diagnosis of FAP, especially without family history, and highlights the importance of a multidisciplinary approach and the adequate study of rare skeletal abnormalities.

Risk of gastric adenoma and adenocarcinoma in patients with familial adenomatous polyposis in Japan: a nationwide multicenter study.

BACKGROUND: Patients with familial adenomatous polyposis (FAP) have an increased risk of developing gastric neoplasms. However, the clinical course of FAP with these gastric lesions has not yet been fully clarified. The present study aimed to clarify the changes in the incidence risk of developing gastric adenoma or gastric cancer during the lifespan of patients with FAP. METHODS: Four hundred forty-three patients with data regarding gastric adenoma and gastric cancer retrospectively registered in a nationwide Japanese multicenter study were enrolled. The cumulative incidences and hazard rates (HRs) of gastric neoplasms were evaluated. RESULTS: The cumulative incidence rates in 50-year-old patients with FAP were 22.8% for gastric adenoma and 7.6% for gastric cancer, respectively. No significant association was found between gastric neoplasms and the colonic phenotype. The peak age for the HR of gastric adenoma was 65 years, with the highest HR (0.043). Regarding the incidence of gastric cancer, the HR increased moderately up to the age of 40 years, but the increase accelerated from the age of 50 years (HR = 0.0067). CONCLUSION: Careful surveillance of the upper gastrointestinal tract in elderly patients with FAP, such as shortening the interval of follow-up according to age, may be helpful for early diagnosis of gastric cancer.

Pathology of Gastrointestinal Polyposis Disorders.

Gastrointestinal polyposis disorders are a group of syndromes defined by clinicopathologic features that include the predominant histologic type of colorectal polyp and specific inherited gene mutations. Adenomatous polyposis syndromes comprise the prototypical familial adenomatous polyposis syndrome and other recently identified genetic conditions inherited in a dominant or recessive manner. Serrated polyposis syndrome is defined by arbitrary clinical criteria. The diagnosis of hamartomatous polyposis syndromes can be suggested from the histologic characteristics of colorectal polyps and the association with various extraintestinal manifestations. Proper identification of affected individuals is important due to an increased risk of gastrointestinal and extragastrointestinal cancers.

The Diagnostic Yield of Genetic Testing in Patients With Multiple Colorectal Adenomas: A Specialist Center Cohort Study.

INTRODUCTION: Adenoma multiplicity is associated with increased colorectal cancer (CRC) risk. The utility of genetic testing in patients with multiple colorectal adenomas (MCRA) remains uncertain. We evaluated the diagnostic yield of mutations in polyposis- and CRC-associated genes in patients with MCRA. METHODS: We performed a cross-sectional review of adult patients with 10-99 cumulative adenomas from the prospective database at the St Mark's Hospital Polyposis Registry and Family Cancer Clinic between 1999 and 2021. Genetic testing was performed for adenomatous polyposis-associated genes, hamartomatous polyposis-associated genes, and nonpolyposis colorectal cancer-associated genes. Clinicopathological outcomes were extracted for multiple logistic regression analysis. RESULTS: Two hundred fifty-nine patients with MCRA (median age 61 [interquartile range 53-69] years) were identified. Sixty-six patients (25.5%) had a pathogenic variant or likely pathogenic variant, with APC and biallelic MUTYH mutations constituting the majority of identified pathogenic variant/likely pathogenic variants. Diagnostic yields were greater than 10% at any adenoma burden. In univariate analysis, higher adenoma burden and younger age were associated with higher yield (both P < 0.0001). In patients with MCRA with 10-19 adenomas without a relevant personal or family history of CRC, the diagnostic yield was nil. In multiple logistic regression analysis, higher adenoma burden, younger age, personal history of CRC, and first-degree familial history of CRC were associated with higher diagnostic yield. DISCUSSION: Diagnostic yield of >10% at any adenoma burden supports current guidance for constitutional genetic testing in patients with MCRA, although the low yield in people older than 60 years with 10-19 adenomas suggests that a stratified approach might be appropriate.

Case Series of Men with the Germline APC I1307K variant and Treatment-Emergent Neuroendocrine Prostate Cancer.

INTRODUCTION: Somatic mutations in the Wnt signaling gene Adenomatous Polyposis Coli (APC) promote metastatic prostate cancer (PCa) progression. Less is known regarding the impact of germline APC mutations on PCa outcomes. We sought to investigate the prevalence of aggressive variant PCa (AVPC) and treatment-emergent neuroendocrine PCa (t-NEPC) in patients with the germline APC I1307K variant, an alteration found in 7% of Ashkenazi Jewish men. MATERIALS AND METHODS: We report a retrospective cohort study comparing patients with PCa and either APC I1307K germline mutation, APC somatic mutations, or unselected patients. Proportions of patients with AVPC among all the cases were estimated along with 95% Clopper-Pearson exact confidence intervals (CI). Odds ratios with 95% CI were provided for the prevalence of t-NEPC and AVPC in patients with germline APC I1307K compared to patients with frameshift alterations in APC. RESULTS: From 2016-2022, 18 patients with PCa at 3 institutions with the germline APC (I1307K) mutation were identified. Clinically-defined AVPC was found in 8 of the 15 cases with metastatic disease (53%; 95% CI: 26%-79%). Combined somatic alterations in two or more of RB1, TP53 or PTEN (molecularly-defined AVPC) were found in 5/18 cases (28%; 95% CI: 10%-54%). When compared to 20 patients with APC somatic frameshift mutations, patients with the germline APC I1307K variant had a significantly increased risk of AVPC (OR 7.2; 95% CI 1.27, 40.68). CONCLUSION: PCa that develops in the presence of the germline APC I1307K mutation appear to be enriched for clinically-defined and molecularly-defined AVPC and in particular, for t-NEPC.

MSH3-related adenomatous polyposis in a patient with the negative family history of colorectal polyps.

Recently, biallelic MSH3 germline pathogenic/likely pathogenic variants have been recognized as a rare cause of adenomatous polyposis. We present a 49-year-old woman who was admitted to our high-risk colorectal cancer clinic after incidental detection of a biallelic MSH3 (likely) pathogenic variant when tested for the germline (likely) pathogenic variants in hereditary breast and ovarian cancer related genes. The focus of this case report is to describe the genotype and phenotype of our patient with MSH3-related adenomatous polyposis. More than half of the polyps (13/19) were located in the right colon. In addition, benign and malignant extraintestinal lesions may be common as our patient had simple liver and kidney cysts and two basal cell skin carcinomas.

Familial Adenomatous Polyposis with Atypical Clinical Morphology and Genetic Variants.

Familial adenomatous polyposis (FAP) is caused by pathogenic variants of the APC gene on the long arm of chromosome 5. An analysis showed an association between germline APC gene variants and clinical signs of FAP; however, attenuated FAP has also been reported in cases with pathogenic variants. In contrast, a phenotype of FAP with no APC germline pathogenic variant and with few signs has been reported. We herein report a 16-year-old girl in whom the presence of multiple large bowel cancers from a young age and several small bowel cancers reflected a carcinogenic tendency higher than that typical for FAP.

Gene-specific ACMG/AMP classification criteria for germline APC variants: Recommendations from the ClinGen InSiGHT Hereditary Colorectal Cancer/Polyposis Variant Curation Expert Panel.

PURPOSE: The Hereditary Colorectal Cancer/Polyposis Variant Curation Expert Panel (VCEP) was established by the International Society for Gastrointestinal Hereditary Tumours and the Clinical Genome Resource, who set out to develop recommendations for the interpretation of germline APC variants underlying Familial Adenomatous Polyposis, the most frequent hereditary polyposis syndrome. METHODS: Through a rigorous process of database analysis, literature review, and expert elicitation, the APC VCEP derived gene-specific modifications to the ACMG/AMP (American College of Medical Genetics and Genomics and Association for Molecular Pathology) variant classification guidelines and validated such criteria through the pilot classification of 58 variants. RESULTS: The APC-specific criteria represented gene- and disease-informed specifications, including a quantitative approach to allele frequency thresholds, a stepwise decision tool for truncating variants, and semiquantitative evaluations of experimental and clinical data. Using the APC-specific criteria, 47% (27/58) of pilot variants were reclassified including 14 previous variants of uncertain significance (VUS). CONCLUSION: The APC-specific ACMG/AMP criteria preserved the classification of well-characterized variants on ClinVar while substantially reducing the number of VUS by 56% (14/25). Moving forward, the APC VCEP will continue to interpret prioritized lists of VUS, the results of which will represent the most authoritative variant classification for widespread clinical use.

A novel APC mutation associated with Gardner syndrome in a Chinese family.

Gardner syndrome (GS) is a specific form of familial adenomatous polyposis (FAP), which manifests as colorectal polyps, multiple osteomas and soft tissue tumors, and in the oral cavity as osteomas of the jaws, odontomas, and abnormal tooth counts. The underlying cause of GS is attributed to mutations in the APC gene. Mutations in this gene disrupt the normal functioning of the protein and lead to the development of GS. To further investigate GS, a family affected by the syndrome was selected from Dongguan, Guangdong Province. The family members underwent a comprehensive survey, which involved collecting clinical data and peripheral venous blood samples. The samples were then used for genetic analysis. Whole exome sequencing (WES) and Sanger sequencing techniques were utilized to screen and identify specific mutation sites in the APC gene. The clinical findings for the GS family included the presence of gastrointestinal polyps and odontomas. After analyzing the genetic sequencing results, a novel mutation site c.4266dupA on the APC gene was found in the patients, which leading to the APC protein truncation. As a result of this study, it is suggested that odontoma may be an early indicator of GS. Additionally, the identification of this novel mutation site in the APC gene expands the known spectrum of genetic mutations associated with the disease. This discovery has significant implications for the early diagnosis of GS, thus enabling timely intervention to reduce the risk of developing colon cancer and other related diseases.

Colibactin mutational signatures in NTHL1 tumor syndrome and MUTYH associated polyposis patients.

Polyketide synthase (pks) island harboring Escherichia coli are, under the right circumstances, able to produce the genotoxin colibactin. Colibactin is a risk factor for the development of colorectal cancer and associated with mutational signatures SBS88 and ID18. This study explores colibactin-associated mutational signatures in biallelic NTHL1 and MUTYH patients. Targeted Next Generation Sequencing (NGS) was performed on colorectal adenomas and carcinomas of one biallelic NTHL and 12 biallelic MUTYH patients. Additional fecal metagenomics and genome sequencing followed by mutational signature analysis was conducted for the NTHL1 patient. Targeted NGS of the NTHL1 patient showed somatic APC variants fitting SBS88 which was confirmed using WGS. Furthermore, fecal metagenomics revealed pks genes. Also, in 1 out of 11 MUTYH patient a somatic variant was detected fitting SBS88. This report shows that colibactin may influence development of colorectal neoplasms in predisposed patients.

Clinical features and distribution of the APC variant in duodenal and ampullary polyps in patients with familial adenomatous polyposis: a multicenter retrospective cohort study in Japan.

BACKGROUND: Management of duodenal or ampullary adenomas in patients with familial adenomatous polyposis (FAP) is a major challenge for clinicians. Insufficient data are available to evaluate the clinical manifestations and distribution of adenomatous polyposis coli (APC) variants in these patients. METHODS: We enrolled 451 patients with data regarding duodenal or ampullary polyps from 632 patients with FAP retrospectively registered in a nationwide Japanese multicenter study. Clinicopathological features and distribution of APC variants were compared between patients with and without duodenal or ampullary polyps. RESULTS: Duodenal and ampullary polyps were found in 59% and 18% of patients with FAP, respectively. The incidence of duodenal cancer was 4.7% in patients with duodenal polyps, and that of ampullary cancer was 18% in patients with ampullary polyps. Duodenal polyps were significantly associated with the presence of ampullary polyps and jejunal/ileal polyps. Duodenal polyps progressed in 35% of patients with a median follow-up of 776 days, mostly in those with early Spigelman stage lesions. Ampullary polyps progressed in 50% of patients with a follow-up of 1484 days. However, only one patient developed a malignancy. The proportion of patients with duodenal polyps was significantly higher among those with intermediate- or profuse-type APC variants than attenuated-type APC variants. The presence of duodenal polyps was significantly associated with ampullary and jejunal/ileal polyps in patients with intermediate- or profuse-type APC variants. CONCLUSIONS: Periodic endoscopic surveillance of the papilla of Vater and small intestine should be planned for patients with FAP with duodenal polyps.

Atypical hypertrophy of retinal pigment epithelium manifesting as the first sign of familial adenomatous polyposis.

A female patient in her 20s presented to a routine ophthalmology appointment. Medical history was unremarkable. Family history was notable for intestinal cancer of a second-degree relative, diagnosed in her late 60s. Fundus examination revealed bilateral, multiple, flat, oval, pigmented lesions with an irregular halo of atrophy. The patient was diagnosed with atypical congenital hypertrophy of retinal pigmented epithelium. Investigation of extraocular associations was performed, including upper and lower endoscopy, which revealed 500-1000 colonic polyps with a maximum size 25 mm. Pathology did not reveal submucosal invasion. Genetic testing detected an adenomatous polyposis coli mutation (heterozygotic variant c.3183_3187delACAAA p.(Gln1062*)).

Region-specific Wnt signaling responses promote gastric polyp formation in patients with familial adenomatous polyposis.

Germline adenomatous polyposis coli (APC) mutation in patients with familial adenomatous polyposis (FAP) promotes gastrointestinal polyposis, including the formation of frequent gastric fundic gland polyps (FGPs). In this study, we investigated how dysregulated Wnt signaling promotes FGPs and why they localize to the corpus region of the stomach. We developed a biobank of FGP and surrounding nonpolyp corpus biopsies and organoids from patients with FAP for comparative studies. Polyp biopsies and polyp-derived organoids exhibited enhanced Wnt target gene expression. Polyp-derived organoids with intrinsically upregulated Wnt signaling showed poor tolerance to further induction, suggesting that high Wnt restricts growth. Targeted genomic sequencing revealed that most gastric polyps did not arise via APC loss of heterozygosity. Studies in genetic mouse models demonstrated that heterozygous Apc loss increased epithelial cell proliferation in the corpus but not the antrum, while homozygous Apc loss was not maintained in the corpus yet induced hyperproliferation in the antrum. Our findings suggest that heterozygous APC mutation in patients with FAP may be sufficient to drive polyp formation in the corpus region while subsequent loss of heterozygosity to further enhance Wnt signaling is not tolerated. This finding contextualizes the abundant yet benign nature of gastric polyps in FAP patient corpus compared with the rare, yet adenomatous polyps in the antrum.