Constitutional mismatch repair deficiency syndrome: clinical description in a French cohort

Germ line genetic NBN variation and predisposition to B-cell acute lymphoblastic leukemia in children

ABSTRACT

Biallelic mutation in the DNA-damage repair gene NBN is the genetic cause of Nijmegen breakage syndrome, which is associated with predisposition to lymphoid malignancies. Heterozygous carriers of germ line NBN variants may also be at risk for leukemia development, although this is much less characterized. By sequencing 4325 pediatric patients with B-cell acute lymphoblastic leukemia (B-ALL), we systematically examined the frequency of germ line NBN variants and identified 25 unique, putatively damaging NBN coding variants in 50 patients. Compared with the frequency of NBN variants in gnomAD noncancer controls (189 unique, putatively damaging NBN coding variants in 472 of 118 479 individuals), we found significant overrepresentation in pediatric B-ALL (P = .004; odds ratio, 1.8). Most B-ALL-risk variants were missense and cluster within the NBN N-terminal domains. Using 2 functional assays, we verified 14 of 25 variants with severe loss-of-function phenotypes and thus classified these as nonfunctional or partially functional. Finally, we found that germ line NBN variant carriers, all of whom were identified as heterozygous genotypes, showed similar survival outcomes relative to those with wild type status. Taken together, our findings provide novel insights into the genetic predisposition to B-ALL, and the impact of NBN variants on protein function and suggest that heterozygous NBN variant carriers may safely receive B-ALL therapy. These trials were registered at www.clinicaltrials.gov as #NCT01225874, NCT00075725, NCT00103285, NCI-T93-0101D, and NCT00137111.

Constitutional mismatch repair deficiency mimicking Lynch syndrome is associated with hypomorphic mismatch repair gene variants

Lynch syndrome (LS) and constitutional mismatch repair deficiency (CMMRD) are distinct cancer syndromes caused, respectively, by mono- and bi-allelic germline mismatch repair (MMR) variants. LS predisposes to mainly gastrointestinal and genitourinary cancers in adulthood. CMMRD predisposes to brain, haematological, and LS-spectrum cancers from childhood. Two suspected LS patients with first cancer diagnosis aged 27 or 38 years were found to be homozygous for an MMR (likely) pathogenic variant, MSH6 c.3226C>T (p.(Arg1076Cys)), or variant of uncertain significance (VUS), MLH1 c.306G>A (p.(Glu102=)). MLH1 c.306G>A was shown to cause leaky exon 3 skipping. The apparent genotype-phenotype conflict was resolved by detection of constitutional microsatellite instability in both patients, a hallmark feature of CMMRD. A hypomorphic effect of these and other variants found in additional late onset CMMRD cases, identified by literature review, likely explains a LS-like phenotype. CMMRD testing in carriers of compound heterozygous or homozygous MMR VUS may find similar cases and novel hypomorphic variants. Individualised management of mono- and bi-allelic carriers of hypomorphic MMR variants is needed until we better characterise the associated phenotypes.

Clinical and biological landscape of constitutional mismatch-repair deficiency syndrome: an International Replication Repair Deficiency Consortium cohort study

BACKGROUND

Constitutional mismatch repair deficiency (CMMRD) syndrome is a rare and aggressive cancer predisposition syndrome. Because a scarcity of data on this condition contributes to management challenges and poor outcomes, we aimed to describe the clinical spectrum, cancer biology, and impact of genetics on patient survival in CMMRD.

METHODS

In this cohort study, we collected cross-sectional and longitudinal data on all patients with CMMRD, with no age limits, registered with the International Replication Repair Deficiency Consortium (IRRDC) across more than 50 countries. Clinical data were extracted from the IRRDC database, medical records, and physician-completed case record forms. The primary objective was to describe the clinical features, cancer spectrum, and biology of the condition. Secondary objectives included estimations of cancer incidence and of the impact of the specific mismatch-repair gene and genotype on cancer onset and survival, including after cancer surveillance and immunotherapy interventions.

FINDINGS

We analysed data from 201 patients (103 males, 98 females) enrolled between June 5, 2007 and Sept 9, 2022. Median age at diagnosis of CMMRD or a related cancer was 8·9 years (IQR 5·9-12·6), and median follow-up from diagnosis was 7·2 years (3·6-14·8). Endogamy among minorities and closed communities contributed to high homozygosity within countries with low consanguinity. Frequent dermatological manifestations (117 [93%] of 126 patients with complete data) led to a clinical overlap with neurofibromatosis type 1 (35 [28%] of 126). 339 cancers were reported in 194 (97%) of 201 patients. The cumulative cancer incidence by age 18 years was 90% (95% CI 80-99). Median time between cancer diagnoses for patients with more than one cancer was 1·9 years (IQR 0·8-3·9). Neoplasms developed in 15 organs and included early-onset adult cancers. CNS tumours were the most frequent (173 [51%] cancers), followed by gastrointestinal (75 [22%]), haematological (61 [18%]), and other cancer types (30 [9%]). Patients with CNS tumours had the poorest overall survival rates (39% [95% CI 30-52] at 10 years from diagnosis; log-rank p<0·0001 across four cancer types), followed by those with haematological cancers (67% [55-82]), gastrointestinal cancers (89% [81-97]), and other solid tumours (96% [88-100]). All cancers showed high mutation and microsatellite indel burdens, and pathognomonic mutational signatures. MLH1 or MSH2 variants caused earlier cancer onset than PMS2 or MSH6 variants, and inferior survival (overall survival at age 15 years 63% [95% CI 55-73] for PMS2, 49% [35-68] for MSH6, 19% [6-66] for MLH1, and 0% for MSH2; p<0·0001). Frameshift or truncating variants within the same gene caused earlier cancers and inferior outcomes compared with missense variants (p<0·0001). The greater deleterious effects of MLH1 and MSH2 variants as compared with PMS2 and MSH6 variants persisted despite overall improvements in survival after surveillance or immune checkpoint inhibitor interventions.

INTERPRETATION

The very high cancer burden and unique genomic landscape of CMMRD highlight the benefit of comprehensive assays in timely diagnosis and precision approaches toward surveillance and immunotherapy. These data will guide the clinical management of children and patients who survive into adulthood with CMMRD.

FUNDING

The Canadian Institutes for Health Research, Stand Up to Cancer, Children's Oncology Group National Cancer Institute Community Oncology Research Program, Canadian Cancer Society, Brain Canada, The V Foundation for Cancer Research, BioCanRx, Harry and Agnieszka Hall, Meagan's Walk, BRAINchild Canada, The LivWise Foundation, St Baldrick Foundation, Hold'em for Life, and Garron Family Cancer Center.

Strategies for diagnosis and management of CMMRD in low-resource countries: report of a Tunisian family

Constitutional Mismatch Repair Deficiency (CMMRD) is a rare childhood cancer predisposition syndrome, caused by biallelic pathogenic germline variants in the mismatch repair genes. Diagnosis and management of this syndrome is challenging, especially in low-resource settings. This study describes a patient diagnosed with colorectal cancer and grade 3 astrocytoma at the age of 11 and 12 respectively. Immunohistochemistry analysis showed a loss of MSH2 and MSH6 protein expression in CRC tissues of the patient. We identified by Targeted Exome Sequencing a homozygous pathogenic germline variant in exon 9 of the MSH6 gene (c.3991 C > T; p.Ala1268Glyfs*6). Genetic investigation of the family showed that the father was heterozygous for the identified pathogenic variant while the brother was wild type for this variant. Our study highlights the importance of a correct and timely diagnosis of CMMRD which can have implications for treatment. It also underlines the imperative need to enhance awareness, diagnostic standards, and surveillance that are crucial for patients and their families.

Whole-body MRI in oncology: A comprehensive review

Whole-Body Magnetic Resonance Imaging (WB-MRI) has cemented its position as a pivotal tool in oncological diagnostics. It offers unparalleled soft tissue contrast resolution and the advantage of sidestepping ionizing radiation. This review explores the diverse applications of WB-MRI in oncology. We discuss its transformative role in detecting and diagnosing a spectrum of cancers, emphasizing conditions like multiple myeloma and cancers with a proclivity for bone metastases. WB-MRI's capability to encompass the entire body in a singular scan has ushered in novel paradigms in cancer screening, especially for individuals harboring hereditary cancer syndromes or at heightened risk for metastatic disease. Additionally, its contribution to the clinical landscape, aiding in the holistic management of multifocal and systemic malignancies, is explored. The article accentuates the technical strides achieved in WB-MRI, its myriad clinical utilities, and the challenges in integration into standard oncological care. In essence, this review underscores the transformative potential of WB-MRI, emphasizing its promise as a cornerstone modality in shaping the future trajectory of cancer diagnostics and treatment.

Immune dysregulation as a leading principle for lymphoma development in diverse immunological backgrounds

Lymphoma is a heterogeneous group of malignancies arising from lymphocytes, which poses a significant challenge in terms of diagnosis and treatment due to its diverse subtypes and underlying mechanisms. This review aims to explore the shared and distinct features of various forms of lymphoma predisposing conditions, with a focus on genetic, immunological and molecular aspects. While diseases such as autoimmune disorders, inborn errors of immunity and iatrogenic immunodeficiencies are biologically and immunologically distinct, each of these diseases results in profound immune dysregulation and a predisposition to lymphoma development. Interestingly, the increased risk is often skewed towards a particular subtype of lymphoma. Patients with inborn errors of immunity in particular present with extreme forms of lymphoma predisposition, providing a unique opportunity to study the underlying mechanisms. External factors such as chronic infections and environmental exposures further modulate the risk of lymphoma development. Common features of conditions predisposing to lymphoma include: persistent inflammation, recurrent DNA damage or malfunctioning DNA repair, impaired tumor surveillance and viral clearance, and dysregulation of fundamental cellular processes such as activation, proliferation and apoptosis. Our growing understanding of the underlying mechanisms of lymphomagenesis provides opportunities for early detection, prevention and tailored treatment of lymphoma development.

A personalized approach to lymphoproliferations in patients with inborn errors of immunity

Biopsies from patients with inborn error of immunity (IEI) may pose a diagnostic challenge due to the abnormal anatomy of their lymphoid organs and the tendency for the development of lymphoproliferations in various organs, some of which may lead to the wrong impression of malignant lymphoma which may prompt aggressive unnecessary treatment. In this article we will review typical histologic findings in various IEI's described in the literature and discuss the appropriate approach to the diagnosis of lymphoproliferations in these patients by presenting illustrative cases.

Constitutional mismatch repair deficiency syndrome with atypical features caused by a homozygous MLH1 missense variant (c.1918C>A, p.(Pro640Thr)): a case report

Constitutional mismatch repair deficiency (CMMRD) syndrome is a rare autosomal recessive genetic disorder caused by biallelic germline mutations in one of the mismatch repair genes. Carriers are at exceptionally high risk for developing, typically in early life, hematological and brain malignancies, as well as cancers observed in Lynch syndrome. We report a homozygous MLH1 missense variant (c.1918C>A p.(Pro640Thr)) in a Tunisian patient with CMMRD syndrome and a family history of early-age colorectal cancer. The proband presented initially with colonic oligopolyposis and adenosquamous carcinoma of the caecum. He later developed several malignancies, including undifferentiated carcinoma of the parotid, grade 4 IDH-mutant astrocytoma, and ampulla of Vater adenocarcinoma. The patient was older than typical for this disease and had a remarkably prolonged survival despite developing four distinct aggressive malignancies. The current report highlights the challenges in assessing the pathogenicity of the identified variant and the remarkable phenotypic diversity in CMMRD.

Constitutional Mismatch Repair Deficiency Syndromes, a Neurofibromatosis 1 Mimicker That Hinders Timely Management

BACKGROUND

Constitutional mismatch repair deficiency (CMMRD) is a rare, autosomal recessive disease caused by a biallelic germline mutation in one of the DNA mismatch repair genes ( MLH1 , MSH2 , MSH6 and PMS2 ). In addition to colorectal, brain, and hematological malignancies, many additional premalignant and non-malignant features that can point toward the diagnosis of CMMRD have been reported. The report from the CMMRD consortium revealed that all children with CMMRD have café-au-lait macules (CALMs) but the number of CALMs does not reach > 5 in all CMMRD patients, which is one of the diagnostic criterions of NF1. About half of the patients with CMMRD develop brain tumors and up to 40% develop metachronous second malignancies.

METHODS

This is an observational retrospective case series describing five pediatric patients with CMMRD.

RESULTS

All the five patients in our cohort developed brain tumors and showed a predilection to the frontal lobe. In our cohort, multiple Mongolian spots, coloboma, obesity, CHD, dysmorphism, and clubfoot were also encountered. In all our patients, NF1 and other tumorigenic predisposing syndromes were initially suspected.

CONCLUSION

Increasing awareness of this condition and its shared reminiscent NF1 features, particularly CALMs among child neurologists, oncologists, geneticists, and dermatologists can help uncover the tip of the iceberg of CMMRD that carries an important consequence on management.

Biomarkers for chemotherapy and drug resistance in the mismatch repair pathway

Drugs targeting DNA repair have developed rapidly in cancer therapy, and numerous inhibitors have already been utilized in preclinical and clinical stages. To optimize the selection of patients for treatment, it is essential to discover biomarkers to anticipate chemotherapy response. The DNA mismatch repair (MMR) pathway is closely correlated with cancer susceptibility and plays an important role in the occurrence and development of cancers. Here, we give a concise introduction of the MMR genes and focus on the potential biomarkers of chemotherapeutic response and resistance. It has been clarified that the status of MMR may affect the outcome of chemotherapy. However, the specific underlying mechanisms as well as contradictory results continue to raise considerable controversy and concern. In this review, we summarize the current literature to provide a general overview.

Genotype-Phenotype Correlations in Autosomal Dominant and Recessive APC Mutation-Negative Colorectal Adenomatous Polyposis

The most prevalent type of intestinal polyposis, colorectal adenomatous polyposis (CAP), is regarded as a precancerous lesion of colorectal cancer with obvious genetic characteristics. Early screening and intervention can significantly improve patients' survival and prognosis. The adenomatous polyposis coli (APC) mutation is believed to be the primary cause of CAP. There is, however, a subset of CAP with undetectable pathogenic mutations in APC, known as APC (-)/CAP. The genetic predisposition to APC (-)/CAP has largely been associated with germline mutations in some susceptible genes, including the human mutY homologue (MUTYH) gene and the Nth-like DNA glycosylase 1 (NTHL1) gene, and DNA mismatch repair (MMR) can cause autosomal recessive APC (-)/CAP. Furthermore, autosomal dominant APC (-)/CAP could occur as a result of DNA polymerase epsilon (POLE)/DNA polymerase delta 1 (POLD1), axis inhibition protein 2 (AXIN2), and dual oxidase 2 (DUOX2) mutations. The clinical phenotypes of these pathogenic mutations vary greatly depending on their genetic characteristics. Therefore, in this study, we present a comprehensive review of the association between autosomal recessive and dominant APC (-)/CAP genotypes and clinical phenotypes and conclude that APC (-)/CAP is a disease caused by multiple genes with different phenotypes and interaction exists in the pathogenic genes.

Genomic Microsatellite Signatures Identify Germline Mismatch Repair Deficiency and Risk of Cancer Onset

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.

MSI colorectal cancer, all you need to know

Colorectal cancer management has been dramatically impacted by molecular profiling these last years. Among these molecular subgroups, patients with microsatellite instability (MSI) are of particular interest, owing to the prognostic and predictive value of this tumor biomarker. This review article explains the molecular abnormalities underlying MSI phenotype and the consequences of such molecular abnormalities on carcinogenesis, genetic instability and immune infiltration. It details the diagnostic methods for identifying MSI colorectal cancer patients and describes how the prognostic and theranostic values of this marker are impacting treatment decision-making for these patients in 2022.

Nervous system (NS) Tumors in Cancer Predisposition Syndromes

Genetic syndromes which develop one or more nervous system (NS) tumors as one of the manifestations can be grouped under the umbrella term of NS tumor predisposition syndromes. Understanding the underlying pathological pathways at the molecular level has led us to many radical discoveries, in understanding the mechanisms of tumorigenesis, tumor progression, interactions with the tumor microenvironment, and development of targeted therapies. Currently, at least 7-10% of all pediatric cancers are now recognized to occur in the setting of genetic predisposition to cancer or cancer predisposition syndromes. Specifically, the cancer predisposition rate in pediatric patients with NS tumors has been reported to be as high as 15%, though it can approach 50% in certain tumor types (i.e., choroid plexus carcinoma associated with Li Fraumeni Syndrome). Cancer predisposition syndromes are caused by pathogenic variation in genes that primarily function as tumor suppressors and proto-oncogenes. These variants are found in the germline or constitutional DNA. Mosaicism, however, can affect only certain tissues, resulting in varied manifestations. Increased understanding of the genetic underpinnings of cancer predisposition syndromes and the ability of clinical laboratories to offer molecular genetic testing allows for improvement in the identification of these patients. The identification of a cancer predisposition syndrome in a CNS tumor patient allows for changes to medical management to be made, including the initiation of cancer surveillance protocols. Finally, the identification of at-risk biologic relatives becomes feasible through cascade (genetic) testing. These fundamental discoveries have also broadened the horizon of novel therapeutic possibilities and have helped to be better predictors of prognosis and survival. The treatment paradigm of specific NS tumors may also vary based on the patient's cancer predisposition syndrome and may be used to guide therapy (i.e., immune checkpoint inhibitors in constitutional mismatch repair deficiency [CMMRD] predisposition syndrome) [8]. Early diagnosis of these cancer predisposition syndromes is therefore critical, in both unaffected and affected patients. Genetic counselors are uniquely trained master's level healthcare providers with a focus on the identification of hereditary disorders, including hereditary cancer, or cancer predisposition syndromes. Genetic counseling, defined as "the process of helping people understand and adapt to the medical, psychological and familial implications of genetic contributions to disease" plays a vital role in the adaptation to a genetic diagnosis and the overall management of these diseases. Cancer predisposition syndromes that increase risks for NS tumor development in childhood include classic neurocutaneous disorders like neurofibromatosis type 1 and type 2 (NF1, NF2) and tuberous sclerosis complex (TSC) type 1 and 2 (TSC1, TSC2). Li Fraumeni Syndrome, Constitutional Mismatch Repair Deficiency, Gorlin syndrome (Nevoid Basal Cell Carcinoma), Rhabdoid Tumor Predisposition syndrome, and Von Hippel-Lindau disease. Ataxia Telangiectasia will also be discussed given the profound neurological manifestations of this syndrome. In addition, there are other cancer predisposition syndromes like Cowden/PTEN Hamartoma Tumor Syndrome, DICER1 syndrome, among many others which also increase the risk of NS neoplasia and are briefly described. Herein, we discuss the NS tumor spectrum seen in the abovementioned cancer predisposition syndromes as with their respective germline genetic abnormalities and recommended surveillance guidelines when applicable. We conclude with a discussion of the importance and rationale for genetic counseling in these patients and their families.

International Consensus Classification of Myeloid Neoplasms and Acute Leukemias: integrating morphologic, clinical, and genomic data

The classification of myeloid neoplasms and acute leukemias was last updated in 2016 within a collaboration between the World Health Organization (WHO), the Society for Hematopathology, and the European Association for Haematopathology. This collaboration was primarily based on input from a clinical advisory committees (CACs) composed of pathologists, hematologists, oncologists, geneticists, and bioinformaticians from around the world. The recent advances in our understanding of the biology of hematologic malignancies, the experience with the use of the 2016 WHO classification in clinical practice, and the results of clinical trials have indicated the need for further revising and updating the classification. As a continuation of this CAC-based process, the authors, a group with expertise in the clinical, pathologic, and genetic aspects of these disorders, developed the International Consensus Classification (ICC) of myeloid neoplasms and acute leukemias. Using a multiparameter approach, the main objective of the consensus process was the definition of real disease entities, including the introduction of new entities and refined criteria for existing diagnostic categories, based on accumulated data. The ICC is aimed at facilitating diagnosis and prognostication of these neoplasms, improving treatment of affected patients, and allowing the design of innovative clinical trials.

Deficient mismatch repair/microsatellite unstable colorectal cancer: Diagnosis, prognosis and treatment

Microsatellite unstable (MSI) colorectal cancers (CRCs) are due to DNA mismatch repair (MMR) deficiency and occurs in15% of non-metastatic diseases and 5% in the metastatic setting. Nearly 30% of MSI CRCs occur in a context of constitutional mutation of the MMR system (Lynch syndrome). Others are sporadic cancers linked to a hypermethylation of the MLH-1 promoter. The pathogenic alterations of MMR genes lead to the accumulation of frequent somatic mutational events and these tumours arbour a high antigen burden and are highly infiltrated with cytotoxic T-cell lymphocytes. Microsatellite instability/DNA mismatch repair deficiency (MSI/dMMR) status has prognostic and predictive implications in non-metastatic and metastatic CRCs. The prognostic value of MSI status in non-metastatic CRCs has been studied extensively, yet the data are more limited for its predictive value in terms of adjuvant chemotherapy efficacy. In both cases (metastatic and non-metastatic settings) treatment with immune check-point inhibitors (ICIs) have shown a remarkable effectiveness in the context of MSI/dMMR status. Indeed, recent data from prospective cohorts and randomised trials have shown a dramatical improvement of survival with immunotherapy (programmed death-ligand 1 [PD-(L)1]   cytotoxic T-lymphocyte-associated antigen 4 [CTLA-4] blockage) in metastatic or non-metastatic MSI/dMMR CRC. In this review we report and discuss how and for whom to test for the MSI/dMMR phenotype, as well as the prognostic value of this phenotype and the new treatment recommendations options for this unique CRC population. Despite their efficacy, primary and secondary resistance to immune checkpoint inhibitors (ICIs) are observed in more than 50% MSI-H/dMMR CRC patients and in the future how to identify these patients and to overcome resistance will be an important challenge.

Tumor predisposition: what's the skin got to do with it?

PURPOSE OF REVIEW

Recognition of skin findings associated with tumor predisposition syndromes can prompt early evaluation and surveillance and improve management. Additionally, knowing when to test and when to defer performing genetic testing can streamline management. This article reviews tumor predisposition syndromes with recently characterized skin findings and disorders for which early recognition and counseling can impact the course of disease.

RECENT FINDINGS

Café au lait macules (CALMs) are important in many tumor predisposition syndromes, and 'atypical' CALMs are associated with constitutional mismatch repair deficiency and Fanconi anemia. Melanoma predisposition syndromes caused by pathogenic variants in POT1 and BAP1 are more recently described, and both are associated with Spitzoid tumors. Somatic pathogenic variants can cause segmental nevoid basal cell carcinoma syndrome and a mosaic form of Peutz-Jeghers syndrome. Patients with PTEN hamartoma syndrome have increased risk for melanoma but this might not occur until adulthood.

SUMMARY

The cutaneous manifestations of tumor predisposition syndromes can aid diagnosis. Early photoprotection is key to modifying a main risk factor for skin cancer in many of these syndromes. Implementing surveillance guidelines facilitates early detection of tumors.

Clinical implications of genetic testing in familial intermediate and late-onset colorectal cancer

The genetic background of familial, late-onset colorectal cancer (CRC) (i.e., onset > age 50 years) has not been studied as thoroughly as other subgroups of familial CRC, and the proportion of families with a germline genetic predisposition to CRC remains to be defined. To define the contribution of known or suggested CRC predisposition genes to familial late-onset CRC, we analyzed 32 well-established or candidate CRC predisposition genes in 75 families with late-onset CRC. We identified pathogenic or likely pathogenic variants in five patients in MSH6 (n = 1), MUTYH (monoallelic; n = 2) and NTHL1 (monoallelic; n = 2). In addition, we identified a number of variants of unknown significance in particular in the lower penetrant Lynch syndrome-associated mismatch repair (MMR) gene MSH6 (n = 6). In conclusion, screening using a comprehensive cancer gene panel in families with accumulation of late-onset CRC appears not to have a significant clinical value due to the low level of high-risk pathogenic variants detected. Our data suggest that only patients with abnormal MMR immunohistochemistry (IHC) or microsatellite instability (MSI) analyses, suggestive of Lynch syndrome, or a family history indicating another cancer predisposition syndrome should be prioritized for such genetic evaluations. Variants in MSH6 and MUTYH have previously been proposed to be involved in digenic or oligogenic hereditary predisposition to CRC. Accumulation of variants in MSH6 and monoallelic, pathogenic variants in MUTYH in our study indicates that digenic or oligogenic inheritance might be involved in late-onset CRC and warrants further studies of complex types of inheritance.

Case Report: Malignant Brain Tumors in Siblings With MSH6 Mutations

Background

Familial brain tumor incidences are low. Identifying the genetic alterations of familial brain tumors can help better understand the pathogenesis and make therapy regimens for these tumors.

Case Presentation

An elder female and a younger male were diagnosed with brain tumors at the age of 10 and 5, respectively. Whole-genome sequencing analysis of the two patients’ blood, primary brain tumor tissues, and their parents’ blood samples was performed, which revealed that the two tumor samples harbored extremely high somatic mutation loads. Additionally, we observed pigmentation on the male patient’s skin.

Conclusion

Germline, biallelic mutation of MSH6—a gene related to DNA mismatch repair whose defect will result in constitutional mismatch repair deficiency (CMMRD)—is causal for the brain tumors of these two siblings.

Risk of somatic hospitalization in parents after cancer in a child, a nationwide cohort study

OBJECTIVE

The diagnosis of cancer in a child is a profoundly stressful experience. The impact on parents' somatic health, including lifestyle-related diseases, however, is unresolved.

METHODS

We conducted a nationwide population- and register-based study with parents of all children under age 20 diagnosed with cancer in Denmark between 1998 - 2013 and parents of cancer-free children, matched (1:10) on child's age and family type. We estimated hazard ratios (HR) with 95% confidence intervals (CI) in Cox proportional hazard models for thirteen major International Classification of Diseases-10 disease-groups, selected stress- and lifestyle-related disease-groups and investigated moderation by time since diagnosis, parental sex, and cancer type.

RESULTS

Among n=7797 parents of children with cancer compared with n=74,388 parents of cancer-free children (51% mothers, mean age 42), we found no overall pattern of increased risk for 13 broad disease-groups. We found increases in digestive system diseases (HR1.06, 95% CI1.01-1.12), genitourinary system diseases (HR 1.08, 95% CI 1.02-1.14), and neoplasms (HR 1.20, 95% CI 1.13-1.27), the latter attributable mostly to increased rates of tobacco-related cancers and mothers' diet-related cancers.

CONCLUSIONS

This is the first attempt to document the impact of childhood cancer on parents' somatic health. With the exception of increased risk for neoplasms, likely due to shared genetic or lifestyle factors, our findings offer the reassuring message, that the burden of caring for a child with cancer does not in general increase parents' risk for somatic diseases. This article is protected by copyright. All rights reserved.

An unusual phenotype occurs in 15% of mismatch repair-deficient tumors and is associated with non-colorectal cancers and genetic syndromes

Immunohistochemistry (IHC) and/or MSI-PCR (microsatellite instability-polymerase chain reaction) tests are performed routinely to detect mismatch repair deficiency (MMR-D). Classical MMR-D tumors present a loss of MLH1/PMS2 or MSH2/MSH6 with MSI-High. Other profiles of MMR-D tumors have been described but have been rarely studied. In this study, we established a classification of unusual MMR-D tumors and determined their frequency and clinical impact. All MMR-D tumors identified between 2007 and 2017 were selected. Any profile besides the classical MMR-D phenotype was defined as unusual. For patients with unusual MMR-D tumors, IHC, and PCR data were reviewed, the tumor mutation burden (TMB) was evaluated and clinical and genetic features were collected. Of the 4948 cases of MMR testing, 3800 had both the available IHC and MSI-PCR results and 585 of these had MMR-D. After reviewing the IHC and PCR, 21% of the cases initially identified as unusual MMR-D were reclassified, which resulted in a final identification of 89 unusual MMR-D tumors (15%). Unusual MMR-D tumors were more often associated with non-CRC than classical MMR-D tumors. Unusual MMR-D tumors were classified into four sub-groups: i) isolated loss of PMS2 or MSH6, ii) classical loss of MLH1/PMS2 or MSH2/MSH6 without MSI, iii) four MMR proteins retained with MSI and, iv) complex loss of MMR proteins, with clinical characteristics for each sub-group. TMB-high or -intermediate was shown in 96% of the cancers studied (24/25), which confirmed MMR deficiency. Genetic syndromes were identified in 44.9% (40/89) and 21.4% (106/496) of patients with unusual and classical MMR-D tumors, respectively (P < 0.001). Five patients treated with an immune checkpoint inhibitor (ICI) had a prolonged clinical benefit. Our classification of unusual MMR-D phenotype helps to identify MMR deficiency. Unusual MMR-D phenotype occurs in 15% of MMR-D tumors. A high frequency of genetic syndromes was noted in these patients who could benefit from ICI.

Mutational burden and immune recognition of gliomas

PURPOSE OF REVIEW

Recent evidence suggests high tumor mutational burden (TMB-H) as a predictor of response to immune checkpoint blockade (ICB) in cancer. However, results in TMB-H gliomas have been inconsistent. In this article, we discuss the main pathways leading to TMB-H in glioma and how these might affect immunotherapy response.

RECENT FINDINGS

Recent characterization of TMB-H gliomas showed that 'post-treatment' related to mismatch repair (MMR) deficiency is the most common mechanism leading to TMB-H in gliomas. Unexpectedly, preliminary evidence suggested that benefit with ICB is rare in this population. Contrary to expectations, ICB response was reported in a subset of TMB-H gliomas associated with constitutional MMR or polymerase epsilon (POLE) defects (e.g., constitutional biallelic MMRd deficiency). In other cancers, several trials suggest increased ICB efficacy is critically associated with increased lymphocyte infiltration at baseline which is missing in most gliomas. Further characterization of the immune microenvironment of gliomas is needed to identify biomarkers to select the patients who will benefit from ICB.

SUMMARY

Intrinsic molecular and immunological differences between gliomas and other cancers might explain the lack of efficacy of ICB in a subset of TMB-H gliomas. Novel combinations and biomarkers are awaited to improve immunotherapy response in these cancers.

Cancer predisposition in pediatric neuro-oncology-practical approaches and ethical considerations

A genetic predisposition to tumor development can be identified in up to 10% of pediatric patients with central nervous system (CNS) tumors. For some entities, the rate of an underlying predisposition is even considerably higher. In recent years, population-based approaches have helped to further delineate the role of cancer predisposition in pediatric oncology. Investigations for cancer predisposition syndrome (CPS) can be guided by clinical signs and family history leading to directed testing of specific genes. The increasingly adopted molecular analysis of tumor and often parallel blood samples with multi-gene panel, whole-exome, or whole-genome sequencing identifies additional patients with or without clinical signs. Diagnosis of a genetic predisposition may put an additional burden on affected families. However, information on a given cancer predisposition may be critical for the patient as potentially influences treatment decisions and may offer the patient and healthy carriers the chance to take part in intensified surveillance programs aiming at early tumor detection. In this review, we discuss some of the practical and ethical challenges resulting from the widespread use of new diagnostic techniques and the most important CPS that may manifest with brain tumors in childhood.

The Second Allele: A Key to Understanding the Timing of Sporadic and Hereditary Colorectal Tumorigenesis

Our understanding of the molecular basis of colorectal neoplasia is derived from Mendelian genetics, with tumor suppressor genes contributing more to the deregulation of growth than oncogenes. In patients with hereditary syndromes, expression of one allele of a key tumor suppressor gene is absent at birth. The loss of the expression of the second allele precipitates tumorigenesis. However, there are multiple ways in which the expression of the second allele of a tumor suppressor gene is lost. Here, we review these ways and their possible effect on phenotype.

Immunohistochemical screening for mismatch repair protein deficiency in paediatric high-grade gliomas - institutional experience and review of literature

PURPOSE

Immunohistochemical (IHC) testing for mismatch repair (MMR) deficiency (MMRD) is used as a screening tool to identify microsatellite instability in various cancers (especially colon). This not only identifies hereditary cancer syndromes like Lynch and constitutional mismatch repair deficiency (CMMRD) but also aids in prognostication and prediction of sensitivity to checkpoint inhibitor drugs. There are very few reported studies on MMRD status of pediatric high-grade gliomas (pHGG) and none from the Indian subcontinent. The aim of this study is to evaluate the frequency of MMRD in pHGG and to assess if there is a need for universal screening with immunohistochemistry.

METHODS

Paraffin blocks of consecutive cases of pHGG (< 18 years) were retrieved from 2 centres, and IHC with four MMR antibodies - MLH1, PMS2, MSH2 and MSH6 - was performed using tissue microarray-based technique.

RESULTS

Three out of nine cases (33%) studied showed loss of staining. One case had loss of MSH2 and MSH6 confirmed by gene sequencing. Eight of the cases were glioblastoma. One case of IDH1-mutated anaplastic astrocytoma showed loss of MLH1 and PMS2 staining. Isolated PMS2 loss was noted in 1 case, where the non-tumour cells also showed loss of staining, indicative CMMRD syndrome. This patient had prior colon cancer with isolated PMS2 loss and responded to check-point inhibitor therapy with nivolumab.

CONCLUSION

Our study shows that the frequency of MMRD to be about one-third of pHGG. Universal IHC screening for MMRD in all pHGGs may benefit early diagnosis and play a role in therapeutic decisions. A larger multi-institutional study will help better assess the prevalence and treatment implications in MMRD tumours.

An isolated childhood myeloid sarcoma with germline MSH6 mutation-a case report

Myeloid sarcoma (MS) is a type of malignant tumor that originates in the bone marrow. This study reports on the treatment of an 11-year-old Uygur girl with a 15-day history of fever and paroxysmal cough, accompanied by right hip pain. During treatment, fatigue and anemia developed, physical strength decreased, and a few petechiae were seen in the lower extremities. Multiple enlarged lymph nodes were palpable in the neck, with slight congestion in the pharynx. Routine blood screening showed three major myeloid lineage abnormalities. Pathological examination revealed the presence of CD10 (-), CD99 (+), CD20 (+), CD3 (-), CD117 (weak+), CD34 (unclear location), TdT (-), Pax5 (-), Ki-67 (50%+), MPO (-), and CD43 (+). The patient was eventually diagnosed with isolated MS. After chemotherapy, no small particles were observed in bone marrow morphology. Complete remission was confirmed by flow cytometric detection of minimal residual disease. Genomic DNA was subjected to targeted sequencing of 236 gene panels to detect somatic mutations and the MSH6 c.3953_3954insAA p.R1318fs germline mutation. Unfortunately, the patient was subsequently lost to follow-up. To our knowledge, an MSH6 germline mutation had not previously been reported in children with MS, and we speculated that an MSH6 germline mutation led to genomic instability, triggering a somatic mutation in multiple genes and ultimately led to the development of MS in this patient. It is suggested that rare base abnormalities may be involved in the development of isolated myeloid sarcomas (IMS).

Genetic predisposition to lymphomas: Overview of rare syndromes and inherited familial variants

Approximately 10 % of malignancies occur in carriers of germline mutations predisposing to cancer. A high risk of developing lymphomas has been noted in many primary immunodeficiencies, including DNA repair disorders. Moreover, implementation of next-generation sequencing has recently enabled to uncover rare genetic variants predisposing patients to lymphoid neoplasms. Some patients harboring inherited predisposition to lymphomas require dedicated clinical management, which will contribute to effective cancer treatment and to the prevention of potential severe toxicities and secondary malignancies. In line with that, our review summarizes the natural history of lymphoid tumors developing on different germline genetic backgrounds and discusses the progress that has been made toward successfully treating these malignancies.

Challenges of Neoantigen Targeting in Lynch Syndrome and Constitutional Mismatch Repair Deficiency Syndrome

Lynch syndrome (LS) and constitutional mismatch repair deficiency (CMMRD) are hereditary disorders characterised by a highly increased risk of cancer development. This is due to germline aberrations in the mismatch repair (MMR) genes, which results in a high mutational load in tumours of these patients, including insertions and deletions in genes bearing microsatellites. This generates microsatellite instability and cause reading frameshifts in coding regions that could lead to the generation of neoantigens and opens up avenues for neoantigen targeting immune therapies prophylactically and therapeutically. However, major obstacles need to be overcome, such as the heterogeneity in tumour formation within and between LS and CMMRD patients, which results in considerable variability in the genes targeted by mutations, hence challenging the choice of suitable neoantigens. The machine-learning methods such as NetMHC and MHCflurry that predict neoantigen- human leukocyte antigen (HLA) binding affinity provide little information on other aspects of neoantigen presentation. Immune escape mechanisms that allow MMR-deficient cells to evade surveillance combined with the resistance to immune checkpoint therapy make the neoantigen targeting regimen challenging. Studies to delineate shared neoantigen profiles across patient cohorts, precise HLA binding algorithms, additional therapies to counter immune evasion and evaluation of biomarkers that predict the response of these patients to immune checkpoint therapy are warranted.

Pediatric Rhabdomyosarcoma: Epidemiology and Genetic Susceptibility

Rhabdomyosarcoma (RMS) is the most common soft-tissue sarcoma in children, yet little is known about its etiology. Studies that examine either environmental exposures or germline genetic predisposition in RMS have begun to identify factors that contribute to this malignancy. Here, we summarize epidemiological reports of RMS incidence in terms of several factors, including age at diagnosis, biological sex, and geographic location. We then describe findings from association studies, which explore the role of parental exposures, birth and perinatal characteristics, and childhood exposures in RMS. Further, we discuss RMS predisposition syndromes and large-scale sequencing studies that have further identified RMS-associated genes. Finally, we propose future directions of study, which aim to advance our understanding of the origin of RMS and can provide knowledge for novel RMS therapies.

Survival Benefit for Individuals With Constitutional Mismatch Repair Deficiency Undergoing Surveillance

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.

Clonal relationship and directionality of progression of synchronous endometrial and ovarian carcinomas in patients with DNA mismatch repair-deficiency associated syndromes

Sporadic synchronous endometrial (ECs) and ovarian cancers (OCs), although clinically considered to be independent primaries, have been shown to be clonally related and likely constitute metastases from each other. We sought to define whether synchronous ECs/OCs in patients with DNA mismatch repair (MMR)-deficiency syndromes would be clonally related. We subjected synchronous ECs/OCs from four patients (LS3-LS6) with clinically confirmed Lynch syndrome (LS) and one patient with constitutional mismatch repair-deficiency syndrome (CMMRD) to massively parallel sequencing targeting 468 cancer-related genes. Somatic mutations, copy number alterations (CNAs), clonal relatedness and clonal decomposition analyses were performed using previously described bioinformatics methods. All synchronous ECs/OCs analyzed were considered independent primaries based on clinicopathologic criteria. Sequencing analysis revealed that the ECs/OCs of three cases (LS2-CMMRD, L3, L4) harbored similar repertoires of somatic mutations and CNAs and were clonally related. In these three cases, a subset of subclonal mutations in the EC became clonal in the OC, suggesting that the EC was likely the substrate from which the OC developed. LS5's EC/OC had distinct mutational profiles but shared specific CNAs. In contrast, LS6's EC/OC harbored distinct somatic mutations and lacked CNAs, consistent with each tumor constituting an independent primary lesion. In LS5 and LS6, PTEN mutations and PTEN loss of protein expression were found to be restricted to the EC. Finally, re-analysis of sequencing data of sporadic synchronous ECs/OCs supported the observations made in the current study that the directionality of progression is likely from the endometrium to the ovary. In conclusion, contrary to sporadic synchronous ECs/OCs, which are almost invariably clonally related, ECs/OCs simultaneously involving the uterus and ovary in LS patients may represent distinct primary tumors. A subset of MMR-deficiency syndrome-related synchronous ECs/OCs, however, may originate from a single primary tumor at variance with their clinical diagnosis, with the endometrium being the likeliest site of origin.

The Challenge of Diagnosing Constitutional Mismatch Repair Deficiency Syndrome in Brain Malignancies from Young Individuals

Biallelic germline mismatch repair (MMR) gene (MLH1, MSH2, MSH6, and PMS2) mutations are an extremely rare event that causes constitutional mismatch repair deficiency (CMMRD) syndrome. CMMRD is underdiagnosed and often debuts with pediatric malignant brain tumors. A high degree of clinical awareness of the CMMRD phenotype is needed to identify new cases. Immunohistochemical (IHC) assessment of MMR protein expression and analysis of microsatellite instability (MSI) are the first tools with which to initiate the study of this syndrome in solid malignancies. MMR IHC shows a hallmark pattern with absence of staining in both neoplastic and non-neoplastic cells for the biallelic mutated gene. However, MSI often fails in brain malignancies. The aim of this report is to draw attention to the peculiar IHC profile that characterizes CMMRD syndrome and to review the difficulties in reaching an accurate diagnosis by describing the case of two siblings with biallelic MSH6 germline mutations and brain tumors. Given the difficulties involved in early diagnosis of CMMRD we propose the use of the IHC of MMR proteins in all malignant brain tumors diagnosed in individuals younger than 25 years-old to facilitate the diagnosis of CMMRD and to select those neoplasms that will benefit from immunotherapy treatment.

Primary cervical glioblastoma multiforme as a presentation of constitutional mismatch repair deficiency: Case report and literature review

Introduction and importance

Primary Glioblastoma Multiforme(GBM) of cervical spinal cord represent an extremely rare type of tumors in the pediatric age group. Constitutional mismatch repair deficiency (CMMRD) patients are known to develop uni- or multiple synchronous-high grade gliomas in the brain.

Case presentation

The authors report a 23 month old child presented with bilateral upper limb weakness for 7 days with imaging evidence of intramedullary mass lesion that extends from the level of the C3 to C7. The patient underwent excisional biopsy from C3 to C7 and laminoplasty. Immunohistology confirmed primary cervical GBM.

Clinical discussion

Constitutional mismatch repair deficiency is cancer tendent syndrome associated with broad spectrum of malignancies. Screening for CMMRD is not a daily practice in oncology and thus prevalence might be underestimated. To authors’ knowledge, no prior primary cervical GBM in CMMRD syndrome.

Conclusion

This report highlights the challenges of CMMRD polymorphic presentations, diagnosis, complications, management and surveillance.

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Primary Glioblastoma of cervical spinal cord tumors represent an extremely rare type of tumors in the pediatric age group.

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CMMRD is a childhood cancer predisposing syndrome caused by germline biallelic autosomal recessive mutations or by compound heterozygous mutations in the MMR genes.

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CMMRD predispose to develop a board spectrum of neuronal origin, hematologic, genitourinary or gastro-intestinal tract tumors.

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CMMRD syndrome patients can have hypo/hyper-pigmentation spots, café-au-lait spots, less frequently freckles and Lisch nodules.

Diagnostic criteria for constitutional mismatch repair deficiency (CMMRD): recommendations from the international consensus working group

BACKGROUND

Constitutional mismatch repair deficiency syndrome (CMMRD) is the most aggressive cancer predisposition syndrome associated with multiorgan cancers, often presenting in childhood. There is variability in age and presentation of cancers and benign manifestations mimicking neurofibromatosis type 1. Genetic testing may not be informative and is complicated by pseudogenes associated with the most commonly associated gene, PMS2. To date, no diagnostic criteria exist. Since surveillance and immune-based therapies are available, establishing a CMMRD diagnosis is key to improve survival.

METHODS

In order to establish a robust diagnostic path, a multidisciplinary international working group, with representation from the two largest consortia (International Replication Repair Deficiency (IRRD) consortium and European Consortium Care for CMMRD (C4CMMRD)), was formed to establish diagnostic criteria based on expertise, literature review and consensus.

RESULTS

The working group established seven diagnostic criteria for the diagnosis of CMMRD, including four definitive criteria (strong evidence) and three likely diagnostic criteria (moderate evidence). All criteria warrant CMMRD surveillance. The criteria incorporate germline mismatch repair results, ancillary tests and clinical manifestation to determine a diagnosis. Hallmark cancers for CMMRD were defined by the working group after extensive literature review and consultation with the IRRD and C4CMMRD consortia.

CONCLUSIONS

This position paper summarises the evidence and rationale to provide specific guidelines for CMMRD diagnosis, which necessitates appropriate surveillance and treatment.

Immune Checkpoint Inhibition as Primary Adjuvant Therapy for an IDH1-Mutant Anaplastic Astrocytoma in a Patient with CMMRD: A Case Report-Usage of Immune Checkpoint Inhibition in CMMRD

Constitutional mismatch repair deficiency (CMMRD) is a rare autosomal recessive hereditary cancer syndrome due to biallelic germline mutation involving one of the four DNA mismatch repair genes. Here we present a case of a young female with CMMRD, homozygous for the c.2002A>G mutation in the PMS2 gene. She developed an early stage adenocarcinoma of the colon at the age of 14. Surveillance MRI of the brain at age 18 resulted in the detection of an asymptomatic brain cancer. On resection, this was diagnosed as an anaplastic astrocytoma. Due to emerging literature suggesting benefit of immunotherapy in this patient population, she was treated with adjuvant dual immune checkpoint inhibition, avoiding radiation. The patient remains stable with no evidence of progression 20 months after resection. The patient’s clinical course, as well as the rational for considering adjuvant immunotherapy in patients with CMMRD are discussed in this report.

Diagnosis of Lynch Syndrome and Strategies to Distinguish Lynch-Related Tumors from Sporadic MSI/dMMR Tumors

Simple Summary

Microsatellite instability (MSI) is a hallmark of Lynch syndrome (LS)-related tumors but is not specific, as most of MSI/mismatch repair-deficient (dMMR) tumors are sporadic. Therefore, the identification of MSI/dMMR requires additional diagnostic tools to identify LS. In this review, we address the hallmarks of LS and present recent advances in diagnostic and screening strategies to identify LS patients. We also discuss the pitfalls associated with current strategies, which should be taken into account in order to improve the diagnosis of LS.

Abstract

Microsatellite instability (MSI) is a hallmark of Lynch syndrome (LS)-related tumors but is not specific to it, as approximately 80% of MSI/mismatch repair-deficient (dMMR) tumors are sporadic. Methods leading to the diagnosis of LS have considerably evolved in recent years and so have tumoral tests for LS screening and for the discrimination of LS-related to MSI-sporadic tumors. In this review, we address the hallmarks of LS, including the clinical, histopathological, and molecular features. We present recent advances in diagnostic and screening strategies to identify LS patients. We also discuss the pitfalls associated with the current strategies, which should be taken into account to improve the diagnosis of LS and avoid inappropriate clinical management.

Non-Hodgkin's Lymphoma and Colorectal Carcinoma: Metachronous Occurrence in a Patient With Underlying DNA Mismatch Repair Syndrome

Constitutional mismatch repair deficiency (CMMRD) is an autosomal recessive disorder caused by biallelic mutations in DNA mismatch repair genes 1. These patients have clinical stigmata of neurofibromatosis 1 (NF-1) with childhood onset of hematological malignancies, high grade gliomas, and colorectal-cancers 2. We present a case of non-Hodgkin's lymphoma (NHL) who later on developed adenocarcinoma colon at an age of 11 years with significant family history of glioblastoma in elder brother and colonic cancer in mother. This is the first case of CMMRD in Pakistan who developed colonic neoplasm at the age of 11 years. Nearly 150 patients of CMMRD have been reported worldwide.

Constitutional Mismatch Repair Deficiency Syndrome in a patient from India

This report highlights an extremely rare genetic condition constitutional mismatch repair deficiency (CMMRD) in an Indian pediatric patient with dual malignancies, who suffered from transient encephalopathy, a rare side effect of the drug Nivolumab and the associated challenge during CSF protein electrophoresis interpretation.

Genetic Susceptibility to Endometrial Cancer: Risk Factors and Clinical Management

Endometrial cancer (EC) is the most common cancer affecting the female reproductive organs in higher-income states. Apart from reproductive factors and excess weight, genetic predisposition is increasingly recognized as a major factor in endometrial cancer risk. Endometrial cancer is genetically heterogeneous: while a subgroup of patients belongs to cancer predisposition syndromes (most notably the Lynch Syndrome) with high to intermediate lifetime risks, there are also several common genomic polymorphisms contributing to the spectrum of germline predispositions. Germline variants and somatic events may act in concert to modulate the molecular evolution of the tumor, where mismatch-repair deficiency is common in endometrioid endometrial tumors whereas homologous recombinational repair deficiency has been described for non-endometrioid endometrial tumors. In this review, we will survey the currently known genomic predispositions for endometrial cancer and discuss their relevance for clinical management in terms of counseling, screening and novel treatments.

An update on the CNS manifestations of brain tumor polyposis syndromes

Cancer predisposition syndromes are associated with an increased risk of developing primary malignancies. Here we discuss those which are associated with an increased risk of tumors of the central nervous system (CNS) and gastrointestinal (GI) tract. These can be grouped into those in which the CNS tumors predominate versus those in which the GI cancers predominate. The former include constitutional mismatch repair deficiency (CMMRD) syndrome, Li-Fraumeni syndrome (LFS), and Cowden syndrome (CS) while the latter include familial adenomatosis polyposis 1 (FAP1), Lynch syndrome and polymerase proofreading-associated polyposis syndrome (PPAP). Tumor specificity does exist as medulloblastoma occur in FAP, LFS and CMMRD while glioma are most commonly seen in all replication repair-deficient genes and LFS. Choroid plexus carcinoma is strictly observed in LFS while Cowden syndrome patients develop Lhermitte Duclos disease or meningioma. In each syndrome, specific types of low-grade and high-grade gastrointestinal cancers can occur, but these will be discussed elsewhere. Underlying cancer predisposition syndromes are important to consider when faced with brain tumors, particularly in the pediatric and young adult age groups, as identification of an underlying germ line mutation may change the upfront management of the patient and has implications for future cancer surveillance for both the patient and potentially affected family members. Considerations of family history, presence of skin lesions and consanguinity provide valuable information in identifying patients at potential increased risk.

Café au Lait Macules and Associated Genetic Syndromes

Café au lait macules (CALMs) are a common, isolated dermatologic finding in the general population. But when do these irregularly shaped, jagged-edged, flat, hyperpigmented birthmarks suggest something that may warrant referral? Most pediatric providers are familiar with the association of CALMs and neurofibromatosis type 1. There are, however, other genetic conditions associated with these seemingly benign skin spots. This article provides an overview of CALMs, followed by a summary of several conditions associated with CALMs ranging from the most common (neurofibromatosis type 1) to rare, ring chromosome syndromes. It reviews the associated gene(s), pattern of inheritance, incidence, presenting symptoms, diagnosis, and management for these genetic conditions.

Recent advances in genetic predisposition to pediatric acute lymphoblastic leukemia

Introduction: Historically, the majority of childhood cancers, including acute lymphoblastic leukemia (ALL), were not thought to have a hereditary basis. However, recent germline genomic studies have revealed that at least 5 - 10% of children with cancer (and approximately 3 - 4% of children with ALL) develop the disease due to an underlying genetic predisposition.Areas covered: This review discusses several recently identified ALL predisposing conditions and provides updates on other more well-established syndromes. It also covers topics related to the evaluation and management of children and family members at increased ALL risk.Expert opinion: Germline predisposition is gaining recognition as an important risk factor underlying the development of pediatric ALL. The challenge now lies in how best to capitalize on germline genetic information to improve ALL diagnosis, treatment, and perhaps even prevention.

DNA Repair Syndromes and Cancer: Insights Into Genetics and Phenotype Patterns

DNA damage response is essential to human physiology. A broad spectrum of pathologies are displayed by individuals carrying monoallelic or biallelic loss-of-function mutations in DNA damage repair genes. DNA repair syndromes with biallelic disturbance of essential DNA damage response pathways manifest early in life with multi-systemic involvement and a high propensity for hematologic and solid cancers, as well as bone marrow failure. In this review, we describe classic biallelic DNA repair cancer syndromes arising from faulty single- and double-strand DNA break repair, as well as dysfunctional DNA helicases. These clinical entities include xeroderma pigmentosum, constitutional mismatch repair deficiency, ataxia telangiectasia, Nijmegen breakage syndrome, deficiencies of DNA ligase IV, NHEJ/Cernunnos, and ERCC6L2, as well as Bloom, Werner, and Rothmund-Thompson syndromes. To give an in-depth understanding of these disorders, we provide historical overview and discuss the interplay between complex biology and heterogeneous clinical manifestations.

Constitutional mismatch repair deficiency-associated brain tumors: report from the European C4CMMRD consortium

Background

Malignant brain tumors (BT) are among the cancers most frequently associated with constitutional mismatch repair deficiency (CMMRD), a rare childhood cancer predisposition syndrome resulting from biallelic germline mutations in mismatch repair genes. This study analyzed data from the European “Care for CMMRD” (C4CMMRD) database to describe their clinical characteristics, treatments, and outcome with the aim of improving its diagnosis/treatment.

Methods

Retrospective analysis of data on patients with CMMRD and malignant BT from the C4CMMRD database up to July 2017.

Results

Among the 87 registered patients, 49 developed 56 malignant BTs: 50 high-grade gliomas (HGG) (with giant multinucleated cells in 16/21 histologically reviewed tumors) and 6 embryonal tumors. The median age at first BT was 9.2 years [1.1–40.6], with nine patients older than 18. Twenty-seven patients developed multiple malignancies (including16 before the BT). Most patients received standard treatment, and eight patients immunotherapy for relapsed HGG. The 3- and 5-year overall survival (OS) rates were 30% (95% CI: 19–45) and 22% (95% CI: 12–37) after the first BT, with worse prognosis for HGG (3-year OS = 20.5%). Six patients were alive (median follow-up 2.5 years) and 43 dead (38 deaths, 88%, were BT-related). Other CMMRD-specific features were café-au-lait macules (40/41), multiple BTs (5/15), developmental brain anomalies (11/15), and consanguinity (20/38 families).

Conclusions

Several characteristics could help suspecting CMMRD in pediatric malignant BTs: giant cells on histology, previous malignancies, parental consanguinity, café-au-lait macules, multiple BTs, and developmental brain anomalies. The prognosis of CMMRD-associated BT treated with standard therapies is poor requiring new therapeutic up-front approaches.

Review: Ewing Sarcoma Predisposition

Ewing sarcoma is a rare tumor developed in bone and soft tissues of children and teenagers. This entity is biologically led by a chromosomal translocation, typically including EWS and FLI1 genes. Little is known about Ewing sarcoma predisposition, although the role of environmental factors, ethnicity and certain polymorphisms on Ewing sarcoma susceptibility has been studied during the last few years. Its prevalence among cancer predisposition syndromes has also been thoroughly examined. This review summarizes the available evidence on predisposing factors involved in Ewing sarcoma susceptibility. On the basis of these data, an integrated approach of the most influential factors on Ewing sarcoma predisposition is proposed.

Integrative Molecular Analysis of Patients With Advanced and Metastatic Cancer

PURPOSE

We developed a precision medicine program for patients with advanced cancer using integrative whole-exome sequencing and transcriptome analysis.

PATIENTS AND METHODS

Five hundred fifteen patients with locally advanced/metastatic solid tumors were prospectively enrolled, and paired tumor/normal sequencing was performed. Seven hundred fifty-nine tumors from 515 patients were evaluated.

RESULTS

Most frequent tumor types were prostate (19.4%), brain (16.5%), bladder (15.4%), and kidney cancer (9.2%). Most frequently altered genes were TP53 (33%), CDKN2A (11%), APC (10%), KTM2D (8%), PTEN (8%), and BRCA2 (8%). Pathogenic germline alterations were present in 10.7% of patients, most frequently CHEK2 (1.9%), BRCA1 (1.5%), BRCA2 (1.5%), and MSH6 (1.4%). Novel gene fusions were identified, including a RBM47-CDK12 fusion in a metastatic prostate cancer sample. The rate of clinically relevant alterations was 39% by whole-exome sequencing, which was improved by 16% by adding RNA sequencing. In patients with more than one sequenced tumor sample (n = 146), 84.62% of actionable mutations were concordant.

CONCLUSION

Integrative analysis may uncover informative alterations for an advanced pan-cancer patient population. These alterations are consistent in spatially and temporally heterogeneous samples.

Repertoire Sequencing of B Cells Elucidates the Role of UNG and Mismatch Repair Proteins in Somatic Hypermutation in Humans

The generation of high-affinity antibodies depends on somatic hypermutation (SHM). SHM is initiated by the activation-induced cytidine deaminase (AID), which generates uracil (U) lesions in the B-cell receptor (BCR) encoding genes. Error-prone processing of U lesions creates a typical spectrum of point mutations during SHM. The aim of this study was to determine the molecular mechanism of SHM in humans; currently available knowledge is limited by the number of mutations analyzed per patient. We collected a unique cohort of 10 well-defined patients with bi-allelic mutations in genes involved in base excision repair (BER) (UNG) or mismatch repair (MMR) (MSH2, MSH6, or PMS2) and are the first to present next-generation sequencing (NGS) data of the BCR, allowing us to study SHM extensively in humans. Analysis using ARGalaxy revealed selective skewing of SHM mutation patterns specific for each genetic defect, which are in line with the five-pathway model of SHM that was recently proposed based on mice data. However, trans-species comparison revealed differences in the role of PMS2 and MSH2 in strand targeting between mice and man. In conclusion, our results indicate a role for UNG, MSH2, MSH6, and PMS2 in the generation of SHM in humans comparable to their function in mice. However, we observed differences in strand targeting between humans and mice, emphasizing the importance of studying molecular mechanisms in a human setting. The here developed method combining NGS and ARGalaxy analysis of BCR mutation data forms the basis for efficient SHM analyses of other immune deficiencies.