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Polypectomy is the most common therapeutic endoscopic intervention in children. Management of sporadic juvenile polyps is limited to polypectomy to resolve symptoms, whereas polyposis syndromes pose a multidisciplinary challenge with broader ramifications. In preparation for polypectomy, there are key patient, polyp, endoscopy unit, and provider characteristics that factor into the likelihood of success. Younger age and multiple medical comorbidities increase the risk of adverse outcomes, classified as intraoperative, immediate postoperative, and delayed postoperative complications. Novel techniques, including cold snare polypectomy, can significantly decrease adverse events but a more structured training process for polypectomy in pediatric gastroenterology is needed., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Purpose: Diagnosis of Mismatch Repair Deficiency (MMRD) is crucial for tumor management and early detection in patients with the cancer predisposition syndrome constitutional mismatch repair deficiency (CMMRD). Current diagnostic tools are cumbersome and inconsistent both in childhood cancers and in determining germline MMRD., Patients and Methods: We developed and analyzed a functional Low-pass Genomic Instability Characterization (LOGIC) assay to detect MMRD. The diagnostic performance of LOGIC was compared with that of current established assays including tumor mutational burden, immunohistochemistry, and the microsatellite instability panel. LOGIC was then applied to various normal tissues of patients with CMMRD with comprehensive clinical data including age of cancer presentation., Results: Overall, LOGIC was 100% sensitive and specific in detecting MMRD in childhood cancers (N = 376). It was more sensitive than the microsatellite instability panel (14%, P = 4.3 × 10 -12 ), immunohistochemistry (86%, P = 4.6 × 10 -3 ), or tumor mutational burden (80%, P = 9.1 × 10 -4 ). LOGIC was able to distinguish CMMRD from other cancer predisposition syndromes using blood and saliva DNA ( P < .0001, n = 277). In normal cells, MMRDness scores differed between tissues (GI > blood > brain), increased over time in the same individual, and revealed genotype-phenotype associations within the mismatch repair genes. Importantly, increased MMRDness score was associated with younger age of first cancer presentation in individuals with CMMRD ( P = 2.2 × 10 -5 )., Conclusion: LOGIC was a robust tool for the diagnosis of MMRD in multiple cancer types and in normal tissues. LOGIC may inform therapeutic cancer decisions, provide rapid diagnosis of germline MMRD, and support tailored surveillance for individuals with CMMRD.

The gastrointestinal hamartomatous polyposis syndromes are rare, autosomal dominant disorders associated with an increased risk of benign and malignant intestinal and extraintestinal tumors. They include Peutz-Jeghers syndrome, juvenile polyposis syndrome, the PTEN hamartoma tumor syndrome (including Cowden's syndrome and Bannayan-Riley-Ruvalcaba syndrome), and hereditary mixed polyposis syndrome. Diagnoses are based on clinical criteria and, in some cases, confirmed by demonstrating the presence of a germline pathogenic variant. The best understood hamartomatous polyposis syndrome is Peutz-Jeghers syndrome, caused by germline pathogenic variants in the STK11 gene. The management is focused on prevention of bleeding and mechanical obstruction of the small bowel by polyps and surveillance of organs at increased risk for cancer. Juvenile polyposis syndrome is caused by a germline pathogenic variant in either the SMAD4 or BMPR1A genes, with differing clinical courses. Patients with SMAD4 pathogenic variants may have massive gastric polyposis, which can result in gastrointestinal bleeding and/or protein-losing gastropathy. Patients with SMAD4 mutations usually have the simultaneous occurrence of hereditary hemorrhagic telangiectasia (juvenile polyposis syndrome-hereditary hemorrhagic telangiectasia overlap syndrome) that can result in epistaxis, gastrointestinal bleeding from mucocutaneous telangiectasias, and arteriovenous malformations. Germline pathogenic variants in the PTEN gene cause overlapping clinical phenotypes (known as the PTEN hamartoma tumor syndromes), including Cowden's syndrome and related disorders that are associated with an increased risk of gastrointestinal and colonic polyposis, colon cancer, and other extraintestinal manifestations and cancers. Due to the relative rarity of the hamartomatous polyposis syndromes, recommendations for management are based on few studies. This US Multi-Society Task Force on Colorectal Cancer consensus statement summarizes the clinical features, assesses the current literature, and provides guidance for diagnosis, assessment, and management of patients with the hamartomatous polyposis syndromes, with a focus on endoscopic management., (Copyright © 2022 by The American College of Gastroenterology, American Gastroenterological Association, and the American Society for Gastrointestinal Endoscopy.)

The gastrointestinal hamartomatous polyposis syndromes are rare, autosomal dominant disorders associated with an increased risk of benign and malignant intestinal and extraintestinal tumors. They include Peutz-Jeghers syndrome, juvenile polyposis syndrome, the PTEN hamartoma tumor syndrome (including Cowden's syndrome and Bannayan-Riley-Ruvalcaba syndrome), and hereditary mixed polyposis syndrome. Diagnoses are based on clinical criteria and, in some cases, confirmed by demonstrating the presence of a germline pathogenic variant. The best understood hamartomatous polyposis syndrome is Peutz-Jeghers syndrome, caused by germline pathogenic variants in the STK11 gene. The management is focused on prevention of bleeding and mechanical obstruction of the small bowel by polyps and surveillance of organs at increased risk for cancer. Juvenile polyposis syndrome is caused by a germline pathogenic variant in either the SMAD4 or BMPR1A genes, with differing clinical courses. Patients with SMAD4 pathogenic variants may have massive gastric polyposis, which can result in gastrointestinal bleeding and/or protein-losing gastropathy. Patients with SMAD4 mutations usually have the simultaneous occurrence of hereditary hemorrhagic telangiectasia (juvenile polyposis syndrome-hereditary hemorrhagic telangiectasia overlap syndrome) that can result in epistaxis, gastrointestinal bleeding from mucocutaneous telangiectasias, and arteriovenous malformations. Germline pathogenic variants in the PTEN gene cause overlapping clinical phenotypes (known as the PTEN hamartoma tumor syndromes), including Cowden's syndrome and related disorders that are associated with an increased risk of gastrointestinal and colonic polyposis, colon cancer, and other extraintestinal manifestations and cancers. Due to the relative rarity of the hamartomatous polyposis syndromes, recommendations for management are based on few studies. This U.S. Multi-Society Task Force on Colorectal Cancer consensus statement summarizes the clinical features, assesses the current literature, and provides guidance for diagnosis, assessment, and management of patients with the hamartomatous polyposis syndromes, with a focus on endoscopic management., (Copyright © 2022 American Society for Gastrointestinal Endoscopy, the American Gastroenterological Association, and the American College of Gastroenterology. Published by Elsevier Inc. All rights reserved.)

The gastrointestinal hamartomatous polyposis syndromes are rare, autosomal dominant disorders associated with an increased risk of benign and malignant intestinal and extraintestinal tumors. They include Peutz-Jeghers syndrome, juvenile polyposis syndrome, the PTEN hamartoma tumor syndrome (including Cowden's syndrome and Bannayan-Riley-Ruvalcaba syndrome), and hereditary mixed polyposis syndrome. Diagnoses are based on clinical criteria and, in some cases, confirmed by demonstrating the presence of a germline pathogenic variant. The best understood hamartomatous polyposis syndrome is Peutz-Jeghers syndrome, caused by germline pathogenic variants in the STK11 gene. The management is focused on prevention of bleeding and mechanical obstruction of the small bowel by polyps and surveillance of organs at increased risk for cancer. Juvenile polyposis syndrome is caused by a germline pathogenic variant in either the SMAD4 or BMPR1A genes, with differing clinical courses. Patients with SMAD4 pathogenic variants may have massive gastric polyposis, which can result in gastrointestinal bleeding and/or protein-losing gastropathy. Patients with SMAD4 mutations usually have the simultaneous occurrence of hereditary hemorrhagic telangiectasia (juvenile polyposis syndrome-hereditary hemorrhagic telangiectasia overlap syndrome) that can result in epistaxis, gastrointestinal bleeding from mucocutaneous telangiectasias, and arteriovenous malformations. Germline pathogenic variants in the PTEN gene cause overlapping clinical phenotypes (known as the PTEN hamartoma tumor syndromes), including Cowden's syndrome and related disorders that are associated with an increased risk of gastrointestinal and colonic polyposis, colon cancer, and other extraintestinal manifestations and cancers. Due to the relative rarity of the hamartomatous polyposis syndromes, recommendations for management are based on few studies. This U.S Multi-Society Task Force on Colorectal Cancer consensus statement summarizes the clinical features, assesses the current literature, and provides guidance for diagnosis, assessment, and management of patients with the hamartomatous polyposis syndromes, with a focus on endoscopic management., (Copyright © 2022 American Gastroenterological Association, the American Society for Gastrointestinal Endoscopy, and The American College of Gastroenterology. Published by Elsevier Inc. All rights reserved.)

Purpose: Constitutional mismatch repair deficiency syndrome (CMMRD) is a lethal cancer predisposition syndrome characterized by early-onset synchronous and metachronous multiorgan tumors. We designed a surveillance protocol for early tumor detection in these individuals., Patients and Methods: Data were collected from patients with confirmed CMMRD who were registered in the International Replication Repair Deficiency Consortium. Tumor spectrum, efficacy of the surveillance protocol, and malignant transformation of low-grade lesions were examined for the entire cohort. Survival outcomes were analyzed for patients followed prospectively from the time of surveillance implementation., Results: A total of 193 malignant tumors in 110 patients were identified. Median age of first cancer diagnosis was 9.2 years (range: 1.7-39.5 years). For patients undergoing surveillance, all GI and other solid tumors, and 75% of brain cancers were detected asymptomatically. By contrast, only 16% of hematologic malignancies were detected asymptomatically ( P < .001). Eighty-nine patients were followed prospectively and used for survival analysis. Five-year overall survival (OS) was 90% (95% CI, 78.6 to 100) and 50% (95% CI, 39.2 to 63.7) when cancer was detected asymptomatically and symptomatically, respectively ( P = .001). Patient outcome measured by adherence to the surveillance protocol revealed 4-year OS of 79% (95% CI, 54.8 to 90.9) for patients undergoing full surveillance, 55% (95% CI, 28.5 to 74.5) for partial surveillance, and 15% (95% CI, 5.2 to 28.8) for those not under surveillance ( P < .0001). Of the 64 low-grade tumors detected, the cumulative likelihood of transformation from low-to high-grade was 81% for GI cancers within 8 years and 100% for gliomas in 6 years., Conclusion: Surveillance and early cancer detection are associated with improved OS for individuals with CMMRD., Competing Interests: Hagit N. BarisConsulting or Advisory Role: Sanofi, Igentify LtdSpeakers' Bureau: Sanofi, Takeda, Pfizer Donald BaselHonoraria: BioMarinConsulting or Advisory Role: iQvia Deborah T. BlumenthalConsulting or Advisory Role: AstraZeneca, Novocure, Takeda Miriam BornhorstConsulting or Advisory Role: AstraZeneca/MedImmune Sara RhodeHonoraria: Myriad GeneticsSpeakers' Bureau: Myriad GeneticsTravel, Accommodations, Expenses: Myriad Genetics Roula FarahHonoraria: Novo NordiskConsulting or Advisory Role: Novo Nordisk William D. FoulkesResearch Funding: AstraZeneca David GassEmployment: X4 PharmaceuticalsHonoraria: X4 PharmaceuticalsSpeakers' Bureau: Precisionscientia Heather HampelStock and Other Ownership Interests: Genome MedicalConsulting or Advisory Role: InVitae, Genome Medical, Promega, 23andMe Jordan R. HansfordConsulting or Advisory Role: Bayer Craig HarlosTravel, Accommodations, Expenses: GlaxoSmithKline Nobuko HijiyaHonoraria: NovartisConsulting or Advisory Role: Novartis, IncyteResearch Funding: Pfizer Junne KamiharaStock and Other Ownership Interests: PanTher Therapeutics, ROME Therapeutics, TellBioHonoraria: Pfizer, NanoString Technologies, Third Rock Ventures, Foundation MedicineConsulting or Advisory Role: ROME Therapeutics, Third Rock VenturesResearch Funding: PureTech, Ribon Therapeutics, ACD BiotechnePatents, Royalties, Other Intellectual Property: Patent on drug delivery device licensed to PanTher Therapeutics, Patents on Repeat RNA biomarkers and therapeutics licensed to Rome Therapeutics, Patents on Circulating Tumor Cell Biomarkers Licensed to TellBio Inc Jeffrey KnipsteinEmployment: PRA Health SciencesConsulting or Advisory Role: Atheneum Alvaro LassalettaStock and Other Ownership Interests: Gilead SciencesConsulting or Advisory Role: Shire, Jazz Pharmaceuticals, Roche, ServierTravel, Accommodations, Expenses: Shire, Gilead Sciences Simon C. LingHonoraria: AbbvieResearch Funding: Abbvie, Gilead Sciences Michael P. LinkConsulting or Advisory Role: Incyte, ADC Therapeutics, Lilly, Steba Biotech, Mesoblast, GlaxoSmithKline, SyndaxResearch Funding: Seattle Genetics, Janssen Oncology Rebecca Loret de MolaEmployment: Huron Consulting Maura MassiminoConsulting or Advisory Role: Oncoscience, Novartis Gary MasonEmployment: Janssen Research & Development, MerckStock and Other Ownership Interests: Johnson & Johnson, MerckTravel, Accommodations, Expenses: Janssen Research & Development Kim E. NicholsStock and Other Ownership Interests: IncyteResearch Funding: Incyte/Novartis, Alpine Immune Sciences Enrico OpocherConsulting or Advisory Role: AstraZenecaTravel, Accommodations, Expenses: AstraZeneca Michael OsbornTravel, Accommodations, Expenses: Amgen, Pfizer Benjamin OshrineHonoraria: Mesoblast Alyssa ReddyConsulting or Advisory Role: Novartis, AstraZeneca Lara ReichmanResearch Funding: Illumina Marc RemkeStock and Other Ownership Interests: Bayer, BB Biotech Ventures, BioNTech AG, InVitae, IDEXX Laboratories Kami Wolfe SchneiderOther Relationship: Journal of Genetic Counseling Duncan StearnsConsulting or Advisory Role: AstraZenecaOpen Payments Link: https://openpaymentsdata.cms.gov/physician/792397 Patrick TombocHonoraria: Unicare Health PlanConsulting or Advisory Role: UniCare Health Plan An Van DammeConsulting or Advisory Role: Octapharm, Pfizer, BayerResearch Funding: Johnson & JohnsonTravel, Accommodations, Expenses: Pfizer, Sobi, Shire, Roche Ira WinerResearch Funding: Oncoceutics David S. ZieglerConsulting or Advisory Role: Bayer, AmgenTravel, Accommodations, Expenses: Bayer Cynthia HawkinsConsulting or Advisory Role: BayerPatents, Royalties, Other Intellectual Property: IP for low-grade glioma and sarcoma fusion panels as well as medulloblastoma subgrouping panel David MalkinConsulting or Advisory Role: Bayer Eric BouffetConsulting or Advisory Role: NovartisResearch Funding: Roche, Bristol Myers SquibbNo other potential conflicts of interest were reported.

The RAS/MAPK pathway is an emerging targeted pathway across a spectrum of both adult and pediatric cancers. Typically, this is associated with a single, well-characterized point mutation in an oncogene. Hypermutant tumors that harbor many somatic mutations may obscure the interpretation of such targetable genomic events. We find that replication repair-deficient (RRD) cancers, which are universally hypermutant and affect children born with RRD cancer predisposition, are enriched for RAS/MAPK mutations ( P = 10 -8 ). These mutations are not random, exist in subclones, and increase in allelic frequency over time. The RAS/MAPK pathway is activated both transcriptionally and at the protein level in patient-derived RRD tumors, and these tumors responded to MEK inhibition in vitro and in vivo . Treatment of patients with RAS/MAPK hypermutant gliomas reveals durable responses to MEK inhibition. Our observations suggest that hypermutant tumors may be addicted to oncogenic pathways, resulting in favorable response to targeted therapies. SIGNIFICANCE: Tumors harboring a single RAS/MAPK driver mutation are targeted individually for therapeutic purposes. We find that in RRD hypermutant cancers, mutations in the RAS/MAPK pathway are enriched, highly expressed, and result in sensitivity to MEK inhibitors. Targeting an oncogenic pathway may provide therapeutic options for these hypermutant polyclonal cancers. This article is highlighted in the In This Issue feature, p. 1307 ., (©2021 American Association for Cancer Research.)

Purpose: Constitutional mismatch repair deficiency (CMMRD) is a highly penetrant cancer predisposition syndrome caused by biallelic mutations in mismatch repair (MMR) genes. As several cancer syndromes are clinically similar, accurate diagnosis is critical to cancer screening and treatment. As genetic diagnosis is confounded by 15 or more pseudogenes and variants of uncertain significance, a robust diagnostic assay is urgently needed. We sought to determine whether an assay that directly measures MMR activity could accurately diagnose CMMRD., Patients and Methods: In vitro MMR activity was quantified using a 3'-nicked G-T mismatched DNA substrate, which requires MSH2-MSH6 and MLH1-PMS2 for repair. We quantified MMR activity from 20 Epstein-Barr virus-transformed lymphoblastoid cell lines from patients with confirmed CMMRD. We also tested 20 lymphoblastoid cell lines from patients who were suspected for CMMRD. We also characterized MMR activity from patients with neurofibromatosis type 1, Li-Fraumeni syndrome, polymerase proofreading-associated cancer syndrome, and Lynch syndrome., Results: All CMMRD cell lines had low MMR activity (n = 20; mean, 4.14 ± 1.56%) relative to controls (n = 6; mean, 44.00 ± 8.65%; P < .001). Repair was restored by complementation with the missing protein, which confirmed MMR deficiency. All cases of patients with suspected CMMRD were accurately diagnosed. Individuals with Lynch syndrome (n = 28), neurofibromatosis type 1 (n = 5), Li-Fraumeni syndrome (n = 5), and polymerase proofreading-associated cancer syndrome (n = 3) had MMR activity that was comparable to controls. To accelerate testing, we measured MMR activity directly from fresh lymphocytes, which yielded results in 8 days., Conclusion: On the basis of the current data set, the in vitro G-T repair assay was able to diagnose CMMRD with 100% specificity and sensitivity. Rapid diagnosis before surgery in non-neoplastic tissues could speed proper therapeutic management.

The US Multi-Society Task Force on Colorectal Cancer, with invited experts, developed a consensus statement and recommendations to assist health care providers with appropriate management of patients with biallelic mismatch repair deficiency (BMMRD) syndrome, also called constitutional mismatch repair deficiency syndrome. This position paper outlines what is known about BMMRD, the unique genetic and clinical aspects of the disease, and reviews the current management approaches to this disorder. This article represents a starting point from which diagnostic and management decisions can undergo rigorous testing for efficacy. There is a lack of strong evidence and a requirement for further research. Nevertheless, providers need direction on how to recognize and care for BMMRD patients today. In addition to identifying areas of research, this article provides guidance for surveillance and management. The major challenge is that BMMRD is rare, limiting the ability to accumulate unbiased data and develop controlled prospective trials. The formation of effective international consortia that collaborate and share data is proposed to accelerate our understanding of this disease., (Copyright © 2017 AGA Institute, The American College of Gastroenterology, the American Society for Gastrointestinal Endoscopy, and European Society for Pediatric Gastroenterology, Hepatology, and Nutrition and North American Society for Pediatric Gastroenterology. Published by Elsevier Inc. All rights reserved.)

The US Multi-Society Task Force on Colorectal Cancer, with invited experts, developed a consensus statement and recommendations to assist health care providers with appropriate management of patients with biallelic mismatch repair deficiency (BMMRD) syndrome, also called constitutional mismatch repair deficiency syndrome. This position paper outlines what is known about BMMRD, the unique genetic and clinical aspects of the disease, and reviews the current management approaches to this disorder. This article represents a starting point from which diagnostic and management decisions can undergo rigorous testing for efficacy. There is a lack of strong evidence and a requirement for further research. Nevertheless, providers need direction on how to recognize and care for BMMRD patients today. In addition to identifying areas of research, this article provides guidance for surveillance and management. The major challenge is that BMMRD is rare, limiting the ability to accumulate unbiased data and develop controlled prospective trials. The formation of effective international consortia that collaborate and share data is proposed to accelerate our understanding of this disease.

Purpose: Recurrent glioblastoma multiforme (GBM) is incurable with current therapies. Biallelic mismatch repair deficiency (bMMRD) is a highly penetrant childhood cancer syndrome often resulting in GBM characterized by a high mutational burden. Evidence suggests that high mutation and neoantigen loads are associated with response to immune checkpoint inhibition., Patients and Methods: We performed exome sequencing and neoantigen prediction on 37 bMMRD cancers and compared them with childhood and adult brain neoplasms. Neoantigen prediction bMMRD GBM was compared with responsive adult cancers from multiple tissues. Two siblings with recurrent multifocal bMMRD GBM were treated with the immune checkpoint inhibitor nivolumab., Results: All malignant tumors (n = 32) were hypermutant. Although bMMRD brain tumors had the highest mutational load because of secondary polymerase mutations (mean, 17,740 ± standard deviation, 7,703), all other high-grade tumors were hypermutant (mean, 1,589 ± standard deviation, 1,043), similar to other cancers that responded favorably to immune checkpoint inhibitors. bMMRD GBM had a significantly higher mutational load than sporadic pediatric and adult gliomas and all other brain tumors (P < .001). bMMRD GBM harbored mean neoantigen loads seven to 16 times higher than those in immunoresponsive melanomas, lung cancers, or microsatellite-unstable GI cancers (P < .001). On the basis of these preclinical data, we treated two bMMRD siblings with recurrent multifocal GBM with the anti-programmed death-1 inhibitor nivolumab, which resulted in clinically significant responses and a profound radiologic response., Conclusion: This report of initial and durable responses of recurrent GBM to immune checkpoint inhibition may have implications for GBM in general and other hypermutant cancers arising from primary (genetic predisposition) or secondary MMRD., (© 2016 by American Society of Clinical Oncology.)

Objectives: Hereditary biallelic mismatch repair deficiency (BMMRD) is caused by biallelic mutations in the mismatch repair (MMR) genes and manifests features of neurofibromatosis type 1, gastrointestinal (GI) polyposis, and GI, brain, and hematological cancers. This is the first study to characterize the GI phenotype in BMMRD using both retrospective and prospective surveillance data., Methods: The International BMMRD Consortium was created to collect information on BMMRD families referred from around the world. All patients had germline biallelic MMR mutations or lack of MMR protein staining in normal and tumor tissue. GI screening data were obtained through medical records with annual updates., Results: Thirty-five individuals from seven countries were identified with BMMRD. GI data were available on 24 of 33 individuals (73%) of screening age, totaling 53 person-years. The youngest age of colonic adenomas was 7, and small bowel adenoma was 11. Eight patients had 19 colorectal adenocarcinomas (CRC; median age 16.7 years, range 8-25), and 11 of 18 (61%) CRC were distal to the splenic flexure. Eleven patients had 15 colorectal surgeries (median 14 years, range 9-25). Four patients had five small bowel adenocarcinomas (SBC; median 18 years, range 11-33). Two CRC and two SBC were detected during surveillance within 6-11 months and 9-16 months, respectively, of last consecutive endoscopy. No patient undergoing surveillance died of a GI malignancy. Familial clustering of GI cancer was observed., Conclusions: The prevalence and penetrance of GI neoplasia in children with BMMRD is high, with rapid development of carcinoma. Colorectal and small bowel surveillance should commence at ages 3-5 and 8 years, respectively.

Biallelic mismatch repair deficiency (bMMRD) is a cancer predisposition syndrome affecting primarily individuals from consanguinous families resulting in multiple childhood cancers including high grade gliomas (HGG). This is the first study to assess the prevalence of bMMRD among patients with HGG in countries where consanguinity is high. We collected molecular and clinical information on all children diagnosed with HGG and supratentorial primitive neuroectodermal tumors (sPNET) between 2003 and 2013 at King Hussein Cancer Center, Jordan. Comparison was made to a similar cohort from Toronto. Clinical data regarding presence of café au lait macules(CAL), family history of cancer, consanguinity, pathology and treatment were collected. Tumors were centrally reviewed and tested for MMRD by immunohistochemistry of the corresponding proteins. Forty-two patients fulfilled the inclusion criteria, including 36 with HGG. MMRD was observed in 39% of HGG of whom 79% also lost MMR staining in the corresponding normal cells suggestive of bMMRD. P53 dysfunction was highly enriched in MMR deficient tumors (p = 0.0003).The frequency of MMRD was significantly lower in Toronto cohort (23%, p = 0.03). Both evidence of CAL and consanguinity correlated with bMMRD (p = 0.005 and 0.05,respectively) but family history of cancer didn't. HGG with all three bMMRD risk factors had evidence of MMRD and all children affected by multiple bMMRD related cancers had identical gene loss by immunohistochemical staining. In Jordan, the frequency of clinical and immunohistochemical alterations suggestive of bMMRD in pediatric HGG is high. Genetic testing will enable appropriate counseling and cancer screening to improve survival of these patients., (© 2015 UICC.)

Germline biallelic mismatch repair deficiency (bMMRD) results in a unique cancer predisposition syndrome in which the affected children are susceptible to the development of malignancies, especially brain, gastrointestinal, and lymphoid cancers. Acute myeloblastic leukemia is rarely reported in this syndrome. Here we report the decision-making challenges in a bMMRD child with acute myeloblastic leukemia. Our experience should alert physicians to include bMMRD in the differential diagnosis of a child with hyper/hypopigmented spots and leukemia. Furthermore, the presence of the above and consanguinity emphasizes the need to rule out bMMRD when an allogeneic bone marrow transplant is considered and to enable the surveillance of other family members for earlier detection of cancers in these children.

Background: Hereditary hemorrhagic telangiectasia (HHT) is an autosomal dominant disorder most often caused by mutation in the endoglin or ALK1 genes. A distinct syndrome combines the clinical features of HHT and juvenile polyposis (JP) and has been associated with SMAD4 mutation. The aim of this study was to describe the phenotype of patients with JP-HHT and SMAD4 mutations and to compare this phenotype with HHT or JP patients with mutations other than SMAD4., Methods: Patients prospectively enrolled in the Toronto HHT and JP databases who underwent genotyping were included. The phenotypic characteristics of JP-HHT patients with SMAD4 mutations and patients with mutations other than SMAD4 were analyzed and compared., Results: Three hundred and fifty-eight patients underwent genetic testing (HHT, n = 332; JP, n = 26). Among fourteen patients identified with SMAD4 mutations, ten met the clinical diagnostic criteria for both JP and HHT (71%). Patients with SMAD4 mutations had 100% penetrance of the polyposis phenotype. All patients with JP and SMAD4 mutation had features of HHT. Three JP-HHT patients developed early onset colorectal cancer (CRC) (mean age 28 years). JP-HHT patients with SMAD4 mutation had a significantly higher rate of anemia than HHT patients with mutations other than SMAD4., Conclusions: Patients with HHT and SMAD4 mutations are at significant risk of JP and CRC. The gastrointestinal phenotype is similar to JP patients without SMAD4 mutation. It is essential for HHT patients to undergo genetic testing to determine if they have SMAD4 mutations so that appropriate gastrointestinal screening and surveillance for JP and CRC can be completed.

Background: Colorectal cancer is extremely rare in childhood. Published case series reporting children and adolescents with colorectal cancer have not focused on the underlying genetic aspects of the tumour or genetic susceptibility of the families., Aims: We examined a cohort of patients with early onset colorectal cancer to determine whether a specific genetic predisposition could be elucidated. In particular, we focused on whether DNA mismatch repair gene deficiency which causes hereditary non-polyposis colorectal cancer (HNPCC) could be elucidated., Methods: Patients with colorectal cancer