How Should We Test for Lynch Syndrome? A Review of Current Guidelines and Future Strategies

Real-World Data on Institutional Implementation of Screening for Mismatch Repair Deficiency and Lynch Syndrome in Endometrial Cancer Patients

Lynch syndrome is an inherited tumor syndrome caused by a pathogenic germline variant in DNA mismatch repair genes. As the leading cause of hereditary endometrial cancer, international guidelines recommend universal screening in women with endometrial cancer. However, testing for Lynch syndrome is not yet well established in clinical practice. The aim of this study was to evaluate adherence to our Lynch syndrome screening algorithm. A retrospective, single-center cohort study was conducted of all endometrial cancer patients undergoing surgical treatment at the Bern University Hospital, Switzerland, between 2017 and 2022. Adherence to immunohistochemical analysis of mismatch repair status, and, if indicated, to MLH1 promoter hypermethylation and to genetic counseling and testing was assessed. Of all 331 endometrial cancer patients, 102 (30.8%) were mismatch repair-deficient and 3 (0.9%) patients were diagnosed with Lynch syndrome. Overall screening adherence was 78.2%, with a notable improvement over the six years from 61.4% to 90.6%. A major reason for non-adherence was lack of provider recommendation for testing, with advanced patient age as a potential patient risk factor. Simplification of the algorithm through standardized reflex screening was recommended to provide optimal medical care for those affected and to allow for cascading testing of at-risk relatives.

Genetic testing for familial melanoma

While the average lifetime risk of melanoma worldwide is approximately 3%, those with inherited high-penetrance mutations face an increased lifetime risk of 52-84%. In countries of low melanoma incidence, such as in Southern Europe, familial melanoma genetic testing may be warranted when there are two first degree relatives with a melanoma diagnosis. Testing criteria for high incidence countries such as USA, or with very-high incidence, such as Australia and New Zealand, would require a threshold of 3 to 4 affected family members. A mutation in the most common gene associated with familial melanoma, CDKN2A, is identified in approximately 10-40% of those meeting testing criteria. However, the use of multi-gene panels covering additional less common risk genes can significantly increase the diagnostic yield. Currently, genetic testing for familial melanoma is typically conducted by qualified genetic counsellors, however with increasing demand on testing services and high incidence rate in certain countries, a mainstream model should be considered. With appropriate training, dermatologists are well placed to identify high risk individuals and offer melanoma genetic test in dermatology clinics. Genetic testing should be given in conjunction with pre- and post-test consultation. Informed patient consent should cover possible results, the limitations and implications of testing including inconclusive results, and potential for genetic discrimination. Previous studies reporting on participant outcomes of genetic testing for familial melanoma have found significant improvements in both sun protective behavior and screening frequency in mutation carriers.

Comparison of immediate germline sequencing and multi-step screening for Lynch syndrome detection in high-risk endometrial and colorectal cancer patients

OBJECTIVE

Lynch syndrome (LS) is a hereditary cancer predisposition syndrome with a significantly increased risk of colorectal and endometrial cancers. Current standard practice involves universal screening for LS in patients with newly diagnosed colorectal or endometrial cancer using a multi-step screening protocol (MSP). However, MSP may not always accurately identify LS cases. To address this limitation, we compared the diagnostic performance of immediate germline sequencing (IGS) with MSP in a high-risk group.

METHODS

A total of 31 Taiwanese women with synchronous or metachronous endometrial and colorectal malignancies underwent MSP which included immunohistochemical staining of DNA mismatch repair (MMR) proteins, MLH1 promoter hypermethylation analysis, and germline sequencing to identify pathogenic variants. All patients who were excluded during MSP received germline sequencing for MMR genes to simulate IGS for the detection of LS.

RESULTS

Our findings indicate that IGS surpassed MSP in terms of diagnostic yield (29.0% vs. 19.4%, respectively) and sensitivity (90% vs. 60%, respectively). Specifically, IGS successfully identified nine LS cases, which is 50% more than the number detected through MSP. Additionally, germline methylation analysis revealed one more LS case with constitutional MLH1 promoter hypermethylation, bringing the total LS cases to ten (32.3%). Intriguingly, we observed no significant differences in clinical characteristics or overall survival between patients with and without LS in our cohort.

CONCLUSION

Our study suggests that IGS may potentially offer a more effective approach compared to MSP in identifying LS among high-risk patients. This advantage is evident when patients have been pre-selected utilizing specific clinical criteria.

Sebaceous carcinoma epidemiology, associated malignancies and Lynch/Muir-Torre syndrome screening in England from 2008 to 2018

BACKGROUND

Sebaceous carcinomas (SC) may be associated with the cancer predisposition syndrome Muir-Torre/Lynch syndrome (MTS/LS), identifiable by SC mismatch repair (MMR) screening; however, there is limited data on MMR status of SC.

OBJECTIVE

To describe the epidemiology of SC, copresentation of other cancers, and population level frequency of MMR screening in SC.

METHODS

A population-based retrospective cohort study of SC patients in the National Cancer Registration and Analysis Service in England.

RESULTS

This study included 1077 SC cases (739 extraocular, 338 periocular). Age-standardized incidence rates (ASIR) were higher in men compared with women, 2.74 (95% CI, 2.52-9.69) per 1,000,000 person-years for men versus 1.47 person-years (95% CI, 1.4-1.62) for women. Of the patients, 19% (210/1077) developed at least one MTS/LS-associated malignancy. MMR immunohistochemical screening was performed in only 20% (220/1077) of SC tumors; of these, 32% (70/219) of tumors were MMR deficient.

LIMITATIONS

Retrospective design.

CONCLUSIONS

Incorporation of MMR screening into clinical practice guidelines for the management of SC will increase the opportunity for MTS/LS diagnoses, with implications for cancer surveillance, chemoprevention with aspirin, and immunotherapy treatment targeted to MTS/LS cancers.

"Go ahead and screen" - advice to healthcare systems for routine lynch syndrome screening from interviews with newly diagnosed colorectal cancer patients

BACKGROUND

Lynch syndrome (LS) is the most common cause of inherited colorectal cancer (CRC). Universal tumor screening (UTS) of newly diagnosed CRC cases is recommended to aid in diagnosis of LS and reduce cancer-related morbidity and mortality. However, not all health systems have adopted UTS processes and implementation may be inconsistent due to system and patient-level complexities.

METHODS

To identify barriers, facilitators, and suggestions for improvements of the UTS process from the patient perspective, we conducted in-depth, semi-structured interviews with patients recently diagnosed with CRC, but not screened for or aware of LS. Patients were recruited from eight regionally diverse US health systems. Interviews were conducted by telephone, 60-minutes, audio-recorded, and transcribed. An inductive, constant comparative analysis approach was employed.  RESULTS: We completed 75 interviews across the eight systems. Most participants were white (79%), about half (52%) were men, and the mean age was 60 years. Most self-reported either no (60%) or minimal (40%) prior awareness of LS. Overall, 96% of patients stated UTS should be a routine standard of care for CRC tumors, consistently citing four primary motivations for wanting to know their LS status and engage in the process for LS identification: "knowledge is power"; "family knowledge"; "prevention and detection"; and "treatment and surveillance." Common concerns pertaining to the process of screening for and identifying LS included: creating anticipatory worry for patients, the potential cost and the accuracy of the genetic test, and possibly having one's health insurance coverage impacted by the LS diagnosis. Patients suggested health systems communicate LS results in-person or by phone from a trained expert in LS; offer proactive verbal and written education about LS, the screening steps, and any follow-up surveillance recommendations; and support patients in communicating their LS screening to any of their blood relatives.

CONCLUSION

Our qualitative findings demonstrate patients with CRC have a strong desire for healthcare systems to regularly implement and offer UTS. Patients offer key insights for health systems to guide future implementation and optimization of UTS and other LS screening programs and maximize diagnosis of individuals with LS and improve cancer-related surveillance and outcomes.

TRIAL REGISTRATION

Not available: not a clinical trial.

A Highly Sensitive Pan-Cancer Test for Microsatellite Instability

Microsatellite instability (MSI) is an evolving biomarker for cancer detection and treatment. MSI was first used to identify patients with Lynch syndrome, a hereditary form of colorectal cancer (CRC), but has recently become indispensable in predicting patient response to immunotherapy. To address the need for pan-cancer MSI detection, a new multiplex assay was developed that uses novel long mononucleotide repeat (LMR) markers to improve sensitivity. A total of 469 tumor samples from 20 different cancer types, including 319 from patients with Lynch syndrome, were tested for MSI using the new LMR MSI Analysis System. Results were validated by using deficient mismatch repair (dMMR) status according to immunohistochemistry as the reference standard and compared versus the Promega pentaplex MSI panel. The sensitivity of the LMR panel for detection of dMMR status by immunohistochemistry was 99% for CRC and 96% for non-CRC. The overall percent agreement between the LMR and Promega pentaplex panels was 99% for CRC and 89% for non-CRC tumors. An increased number of unstable markers and the larger size shifts observed in dMMR tumors using the LMR panel increased confidence in MSI determinations. The LMR MSI Analysis System expands the spectrum of cancer types in which MSI can be accurately detected.

Diagnosis of patients with Lynch syndrome lacking the Amsterdam II or Bethesda criteria

BACKGROUND

Lynch Syndrome (LS) is an autosomal dominant inheritance disorder characterized by genetic predisposition to develop cancer, caused by pathogenic variants in the genes of the mismatch repair system. Cases are detected by implementing the Amsterdam II and the revised Bethesda criteria, which are based on family history.

MAIN BODY

Patients who meet the criteria undergo posterior tests, such as germline DNA sequencing, to confirm the diagnosis. However, these criteria have poor sensitivity, as more than one-quarter of patients with LS do not meet the criteria. It is very likely that the lack of sensitivity of the criteria is due to the incomplete penetrance of this syndrome. The penetrance and risk of developing a particular type of cancer are highly dependent on the affected gene and probably of the variant. Patients with variants in low-penetrance genes have a lower risk of developing a cancer associated with LS, leading to families with unaffected generations and showing fewer clear patterns. This study focuses on describing genetic aspects of LS cases that underlie the lack of sensitivity of the clinical criteria used for its diagnosis.

CONCLUSION

Universal screening could be an option to address the problem of underdiagnosis.

ALK, ROS1, RET and NTRK1-3 Gene Fusions in Colorectal and Non-Colorectal Microsatellite-Unstable Cancers

This study aimed to conduct a comprehensive analysis of actionable gene rearrangements in tumors with microsatellite instability (MSI). The detection of translocations involved tests for 5'/3'-end expression imbalance, variant-specific PCR and RNA-based next generation sequencing (NGS). Gene fusions were detected in 58/471 (12.3%) colorectal carcinomas (CRCs), 4/69 (5.8%) gastric cancers (GCs) and 3/65 (4.6%) endometrial cancers (ECs) (ALK: 8; RET: 12; NTRK1: 24; NTRK2: 2; NTRK3: 19), while none of these alterations were observed in five cervical carcinomas (CCs), four pancreatic cancers (PanCs), three cholangiocarcinomas (ChCs) and two ovarian cancers (OCs). The highest frequency of gene rearrangements was seen in KRAS/NRAS/BRAF wild-type colorectal carcinomas (53/204 (26%)). Surprisingly, as many as 5/267 (1.9%) KRAS/NRAS/BRAF-mutated CRCs also carried tyrosine kinase fusions. Droplet digital PCR (ddPCR) analysis of the fraction of KRAS/NRAS/BRAF mutated gene copies in kinase-rearranged tumors indicated that there was simultaneous co-occurrence of two activating events in cancer cells, but not genetic mosaicism. CRC patients aged above 50 years had a strikingly higher frequency of translocations as compared to younger subjects (56/365 (15.3%) vs. 2/106 (1.9%), p = 0.002), and this difference was particularly pronounced for tumors with normal KRAS/NRAS/BRAF status (52/150 (34.7%) vs. 1/54 (1.9%), p = 0.001). There were no instances of MSI in 56 non-colorectal tumors carrying ALK, ROS1, RET or NTRK1 rearrangements. An analysis of tyrosine kinase gene translocations is particularly feasible in KRAS/NRAS/BRAF wild-type microsatellite-unstable CRCs, although other categories of tumors with MSI also demonstrate moderate occurrence of these events.

Microsatellite instability in noncolorectal and nonendometrial malignancies in patients with Lynch syndrome

BACKGROUND

Individuals with Lynch syndrome are at increased hereditary risk of colorectal and endometrial carcinomas with microsatellite instability (MSI-H) and mismatch repair-deficiency (dMMR), which make these tumors vulnerable to therapy with immune checkpoint inhibitors. Our aim is to assess how often other tumor types in these individuals share these characteristics.

METHODS

We retrieved the full tumor history of a historical clinic-based cohort of 1745 individuals with Lynch syndrome and calculated the standardized incidence ratio for all tumor types. MSI status, somatic second hit alterations, and immunohistochemistry-based MMR status were analyzed in 236 noncolorectal and nonendometrial malignant tumors.

RESULTS

In individuals with Lynch syndrome MSI-H/dMMR occurred both in Lynch-spectrum and in non-Lynch-spectrum malignancies (85% vs 37%, P < .01). MSI-H/dMMR malignancies were found in nearly all non-Lynch-spectrum tumor types. Almost all breast carcinomas had medullary features, and most of them were MSI-H/dMMR. Breast carcinoma with medullary features were shown to be associated with Lynch syndrome (standardized incidence ratio = 38.8, 95% confidence interval = 16.7 to 76.5).

CONCLUSIONS

In individuals with Lynch syndrome, MSI-H/dMMR occurs in more than one-half of the malignancies other than colorectal and endometrial carcinomas, including tumor types without increased incidence. The Lynch-spectrum tumors should be expanded to breast carcinomas with medullary features. All malignancies in patients with Lynch syndrome, independent of subtype, should be tested for MSI-H/dMMR in case therapy with immune checkpoint inhibitors is considered. Moreover, Lynch syndrome should be considered an underlying cause of all MSI-H/dMMR malignancies other than colorectal and endometrial carcinomas.

Pathogenic Insights into DNA Mismatch Repair (MMR) Genes-Proteins and Microsatellite Instability: Focus on Adrenocortical Carcinoma and Beyond

DNA damage repair pathways, including mismatch repair (MMR) genes, are prone to carcinoma development in certain patients. The assessment of the MMR system is widely recognized as part of strategies concerning solid tumors (defective MMR cancers), especially MMR proteins (through immunohistochemistry), and molecular assays for microsatellite instability (MSI). We aim to highlight the status of MMR genes-proteins (including MSI) in the relationship with ACC (adrenocortical carcinoma) according to current knowledge. This is a narrative review. We included PubMed-accessed, full-length English papers published between January 2012 and March 2023. We searched studies on ACC patients for whom MMR status was assessed, respectively subjects harboring MMR germline mutations, namely Lynch syndrome (LS), who were diagnosed with ACC. MMR system assessments in ACCs involve a low level of statistical evidence. Generally, there are two main types of endocrine insights: 1. the role of MMR status as a prognostic marker in different endocrine malignancies (including ACC)-which is the topic of the present work, and 2. establishing the indication of immune checkpoint inhibitors (ICPIs) in selective, mostly highly aggressive, non-responsive to standard care forms upon MMR evaluation (which belongs to the larger chapter of immunotherapy in ACCs). Our one-decade, sample-case study (which, to our knowledge, it is the most comprehensive of its kind) identified 11 original articles (from 1 patient to 634 subjects per study diagnosed with either ACC or LS). We identified four studies published in 2013 and 2020 and two in 2021, three cohorts and two retrospective studies (the publication from 2013 includes a retrospective and a cohort distinct section). Among these four studies, patients already confirmed to have LS (N = 643, respective 135) were found to be associated with ACC (N = 3, respective 2), resulting in a prevalence of 0.0046%, with a respective of 1.4% being confirmed (despite not having a large amount of similar data outside these two studies). Studies on ACC patients (N = 364, respective 36 pediatric individuals, and 94 subjects with ACC) showed that 13.7% had different MMR gene anomalies, with a respective of 8.57% (non-germline mutations), while 3.2% had MMR germline mutations (N = 3/94 cases). Two case series included one family, with a respective four persons with LS, and each article introduced one case with LS-ACC. Another five case reports (between 2018 and 2021) revealed an additional five subjects (one case per paper) diagnosed with LS and ACC (female to male ratio of 4 to 1; aged between 44 and 68). Interesting genetic testing involved children with TP53-positive ACC and further MMR anomalies or an MSH2 gene-positive subject with LS with a concurrent germline RET mutation. The first report of LS-ACC referred for PD-1 blockade was published in 2018. Nevertheless, the use of ICPI in ACCs (as similarly seen in metastatic pheochromocytoma) is still limited. Pan-cancer and multi-omics analysis in adults with ACC, in order to classify the candidates for immunotherapy, had heterogeneous results, and integrating an MMR system in this larger and challenging picture is still an open issue. Whether individuals diagnosed with LS should undergo surveillance for ACC has not yet been proven. An assessment of tumor-related MMR/MSI status in ACC might be helpful. Further algorithms for diagnostics and therapy, also taking into consideration innovative biomarkers as MMR-MSI, are necessary.

Mismatch repair deficiency testing in Lynch syndrome-associated urothelial tumors

Introduction

Lynch syndrome-associated cancer develops due to germline pathogenic variants in one of the mismatch repair (MMR) genes, MLH1, MSH2, MSH6 or PMS2. Somatic second hits in tumors cause MMR deficiency, testing for which is used to screen for Lynch syndrome in colorectal cancer and to guide selection for immunotherapy. Both MMR protein immunohistochemistry and microsatellite instability (MSI) analysis can be used. However, concordance between methods can vary for different tumor types. Therefore, we aimed to compare methods of MMR deficiency testing in Lynch syndrome-associated urothelial cancers.

Methods

Ninety-seven urothelial (61 upper tract and 28 bladder) tumors diagnosed from 1980 to 2017 in carriers of Lynch syndrome-associated pathogenic MMR variants and their first-degree relatives (FDR) were analyzed by MMR protein immunohistochemistry, the MSI Analysis System v1.2 (Promega), and an amplicon sequencing-based MSI assay. Two sets of MSI markers were used in sequencing-based MSI analysis: a panel of 24 and 54 markers developed for colorectal cancer and blood MSI analysis, respectively.

Results

Among the 97 urothelial tumors, 86 (88.7%) showed immunohistochemical MMR loss and 68 were successfully analyzed by the Promega MSI assay, of which 48 (70.6%) were MSI-high and 20 (29.4%) were MSI-low/microsatellite stable. Seventy-two samples had sufficient DNA for the sequencing-based MSI assay, of which 55 (76.4%) and 61 (84.7%) scored as MSI-high using the 24-marker and 54-marker panels, respectively. The concordance between the MSI assays and immunohistochemistry was 70.6% (p = 0.003), 87.5% (p = 0.039), and 90.3% (p = 1.00) for the Promega assay, the 24-marker assay, and the 54-marker assay, respectively. Of the 11 tumors with retained MMR protein expression, four were MSI-low/MSI-high or MSI-high by the Promega assay or one of the sequencing-based assays.

Conclusion

Our results show that Lynch syndrome-associated urothelial cancers frequently had loss of MMR protein expression. The Promega MSI assay was significantly less sensitive, but the 54-marker sequencing-based MSI analysis showed no significant difference compared to immunohistochemistry. Data from this study alongside previous studies, suggest that universal MMR deficiency testing of newly diagnosed urothelial cancers, using immunohistochemistry and/or sequencing-based MSI analysis of sensitive markers, offer a potentially useful approach to identification of Lynch syndrome cases.

Constitutional Microsatellite Instability, Genotype, and Phenotype Correlations in Constitutional Mismatch Repair Deficiency

BACKGROUND & AIMS

Constitutional mismatch repair deficiency (CMMRD) is a rare recessive childhood cancer predisposition syndrome caused by germline mismatch repair variants. Constitutional microsatellite instability (cMSI) is a CMMRD diagnostic hallmark and may associate with cancer risk. We quantified cMSI in a large CMMRD patient cohort to explore genotype-phenotype correlations using novel MSI markers selected for instability in blood.

METHODS

Three CMMRD, 1 Lynch syndrome, and 2 control blood samples were genome sequenced to >120× depth. A pilot cohort of 8 CMMRD and 38 control blood samples and a blinded cohort of 56 CMMRD, 8 suspected CMMRD, 40 Lynch syndrome, and 43 control blood samples were amplicon sequenced to 5000× depth. Sample cMSI score was calculated using a published method comparing microsatellite reference allele frequencies with 80 controls.

RESULTS

Thirty-two mononucleotide repeats were selected from blood genome and pilot amplicon sequencing data. cMSI scoring using these MSI markers achieved 100% sensitivity (95% CI, 93.6%-100.0%) and specificity (95% CI 97.9%-100.0%), was reproducible, and was superior to an established tumor MSI marker panel. Lower cMSI scores were found in patients with CMMRD with MSH6 deficiency and patients with at least 1 mismatch repair missense variant, and patients with biallelic truncating/copy number variants had higher scores. cMSI score did not correlate with age at first tumor.

CONCLUSIONS

We present an inexpensive and scalable cMSI assay that enhances CMMRD detection relative to existing methods. cMSI score is associated with mismatch repair genotype but not phenotype, suggesting it is not a useful predictor of cancer risk.

Tumor-independent Detection of Inherited Mismatch Repair Deficiency for the Diagnosis of Lynch Syndrome with High Specificity and Sensitivity

Lynch syndrome (LS) is the most common hereditary cancer syndrome. Early diagnosis improves prognosis and reduces health care costs, through existing cancer surveillance methods. The problem is finding and diagnosing the cancer predisposing genetic condition. The current workup involves a complex array of tests that combines family cancer history and clinical phenotypes with tumor characteristics and sequencing data, followed by a challenging task to interpret the found variant(s). On the basis of the knowledge that an inherited mismatch repair (MMR) deficiency is a hallmark of LS, we have developed and validated a functional MMR test, DiagMMR, that detects inherited MMR deficiency directly from healthy tissue without need of tumor and variant information. The validation included 119 skin biopsies collected from clinically pathogenic MMR variant carriers (MSH2, MSH6) and controls, and was followed by a small clinical pilot study. The repair reaction was performed on proteins extracted from primary fibroblasts and the interpretation was based on the MMR capability of the sample in relation to cutoff, which distinguishes MMR proficient (non-LS) from MMR deficient (LS) function. The results were compared with the reference standard (germline NGS). The test was shown to have exceptional specificity (100%) with high sensitivity (89%) and accuracy (97%). The ability to efficiently distinguish LS carriers from controls was further shown with a high area under the receiving operating characteristic (AUROC) value (0.97). This test offers an excellent tool for detecting inherited MMR deficiency linked to MSH2 or MSH6 and can be used alone or with conventional tests to recognize genetically predisposed individuals.

SIGNIFICANCE

Clinical validation of DiagMMR shows high accuracy in distinguishing individuals with hereditary MSH2 or MSH6 MMR deficiency (i.e., LS). The method presented overcomes challenges faced by the complexity of current methods and can be used alone or with conventional tests to improve the ability to recognize genetically predisposed individuals.

Cancer prevention in cancer predisposition syndromes: A protocol for testing the feasibility of building a hereditary cancer research registry and nurse navigator follow up model

Monogenic, high penetrance syndromes, conferring an increased risk of malignancies in multiple organs, are important contributors to the hereditary burden of cancer. Early detection and risk reduction strategies in patients with a cancer predisposition syndrome can save their lives. However, despite evidence supporting the benefits of early detection and risk reduction strategies, most Canadian jurisdictions have not implemented programmatic follow up of these patients. In our study site in the province of Newfoundland and Labrador (NL), Canada, there is no centralized, provincial registry of high-risk individuals. There is no continuity or coordination of care providing cancer genetics expertise and no process to ensure that patients are referred to the appropriate specialists or risk management interventions. This paper describes a study protocol to test the feasibility of obtaining and analyzing patient risk management data, specifically patients affected by hereditary breast ovarian cancer syndrome (HBOC; BRCA 1 and BRCA 2 genes) and Lynch syndrome (LS; MLH1, MSH2, MSH6, and PMS2 genes). Through a retrospective cohort study, we will describe these patients' adherence to risk management guidelines and test its relationship to health outcomes, including cancer incidence and stage. Through a qualitative interviews, we will determine the priorities and preferences of patients with any inherited cancer mutation for a follow up navigation model of risk management. Study data will inform a subsequent funding application focused on creating and evaluating a research registry and follow up nurse navigation model. It is not currently known what proportion of cancer mutation carriers are receiving care according to guidelines. Data collected in this study will provide clinical uptake and health outcome information so gaps in care can be identified. Data will also provide patient preference information to inform ongoing and planned research with cancer mutation carriers.

Functional characterization of MLH1 missense variants unveils mechanisms of pathogenicity and clarifies role in cancer

Lynch syndrome is a heritable condition caused by a heterozygous germline inactivating mutation of the DNA mismatch repair (MMR) genes, most commonly the MLH1 gene. However, one third of the identified alterations are missense variants, for which the clinical significance is unclear in many cases. We have identified three MLH1 missense alterations (p.(Glu736Lys), p.(Pro640Thr) and p.(Leu73Pro)) in six individuals from large Tunisian families. For none of these alterations, a classification of pathogenicity was available, consequently diagnosis, predictive testing and targeted surveillance in affected families was impossible. We therefore performed functional laboratory testing using a system testing stability as well as catalytic activity that includes clinically validated reference variants. Both p.(Leu73Pro) and p.(Pro640Thr) were found to be non-functional due to severe defects in protein stability and catalytic activity. In contrast, p.(Glu736Lys) was comparable to the wildtype protein and therefore considered a neutral substitution. Analysis of residue conservation and of the structural roles of the substituted residues corroborated these findings. In conjunction with the available clinical data, two variants fulfil classification criteria for class 4 "likely pathogenic". The findings of this work clarify the mechanism of pathogenicity of two unclear MLH1 variants and enables predictive testing and targeted surveillance in members of carrier families worldwide.

Detection of Microsatellite Instability in Colonoscopic Biopsies and Postal Urine Samples from Lynch Syndrome Cancer Patients Using a Multiplex PCR Assay

Identification of mismatch repair (MMR)-deficient colorectal cancers (CRCs) is recommended for Lynch syndrome (LS) screening, and supports targeting of immune checkpoint inhibitors. Microsatellite instability (MSI) analysis is commonly used to test for MMR deficiency. Testing biopsies prior to tumour resection can inform surgical and therapeutic decisions, but can be limited by DNA quantity. MSI analysis of voided urine could also provide much needed surveillance for genitourinary tract cancers in LS. Here, we reconfigure an existing molecular inversion probe-based MSI and BRAF c.1799T > A assay to a multiplex PCR (mPCR) format, and demonstrate that it can sample >140 unique molecules per marker from <1 ng of DNA and classify CRCs with 96−100% sensitivity and specificity. We also show that it can detect increased MSI within individual and composite CRC biopsies from LS patients, and within preoperative urine cell free DNA (cfDNA) from two LS patients, one with an upper tract urothelial cancer, the other an undiagnosed endometrial cancer. Approximately 60−70% of the urine cfDNAs were tumour-derived. Our results suggest that mPCR sequence-based analysis of MSI and mutation hotspots in CRC biopsies could facilitate presurgery decision making, and could enable postal-based screening for urinary tract and endometrial tumours in LS patients.

Gynecological Cancers in Lynch Syndrome: A Comparison of the Histological Features with Sporadic Cases of the General Population

Introduction: About 5% of endometrial cancers (ECs) are attributed to an inherited predisposition, for which Lynch syndrome (LS) accounts for the majority of cases. Women with LS have a 40−60% predicted lifetime risk of developing EC, in addition to a 40−80% lifetime risk of developing colorectal cancer and other cancers. In this population, the lifetime risk of developing ovarian cancer (OC) is 10−12%. Object: to compare the histopathological features of LS-associated EC and OC with sporadic cancers in order to evaluate whether there are differences in terms of age at diagnosis, site of occurrence in the uterus, histological type, stage at diagnosis, and tumor grading. Materials and methods: we compared data obtained from 96 patients with LS-associated gynecological cancers (82 with EC and 14 with OC) to a control group (CG) of 209 patients who developed sporadic EC, and a CG of 187 patients with sporadic OC. Results: The mean age at diagnosis of LS-associated EC and OC was much lower than in the control groups. In both groups with EC, the endometrioid histotype was the most frequently occurring histotype. However, among LS women there was a significantly higher incidence of clear cell tumors (11% versus 2.4% in the CG, p = 0.0001). Similar to the sporadic cancer cases, most of the LS-associated ECs presented at an early stage (89% of cases at FIGO I-II stage). In the LS group, the tumor frequently involved only the inner half of the endometrium (77% of cases, p < 0.01). In the LS group, 7.3% of ECs were localized to the lower uterine segment (LUS), whereas no cancer developed in the LUS in the CG. No serous OCs were diagnosed in the LS group (versus 45.5% in the CG, p = 0.0009). Most of the LS-associated OCs presented at an early stage (85% of cases at FIGO I-II stages, p < 0.01). Conclusion: LS-associated EC and OC seem to have peculiar features, occurring at a younger age and at an earlier stage. In LS, EC less frequently involves the outer half of the endometrium, with a more frequent occurrence in the LUS. The presence of clear cell EC was more frequently observed, whereas in OC, the predominant histotype was endometrioid.

A Scoring Model and Protocol to Adapt Universal Screening for Lynch Syndrome to Identify Germline Pathogenic Variants by Next Generation Sequencing from Colorectal Cancer Patients and Cascade Screening

Simple Summary

Lynch syndrome (LS) is an autosomal-dominantly inherited form of cancer predisposition dominated by colorectal cancer (CRC). LS is caused by germline pathogenic variants (PV) occurring in known mismatch repair genes. For effective cascade screening, it is critical to identify PV for LS predisposition. When limited resources are available, next generation sequencing (NGS) of an entire cohort of colorectal cancer (CRC) patients, even those under 50 or 60 years of age, places a huge burden on the system. Here, we present an innovative LS ascertainment and follow-up program that includes LS molecular analysis, PV screening with NGS technology, and cascade screening. The goal is to improve LS ascertainment in light of the growing burden of early-onset CRC, particularly in low- and middle-income countries.

Abstract

Identification of germline pathogenic variants (PV) predisposing to Lynch syndrome (LS) is an important step for effective use of cascade screening of extended at-risk lineages, leading to reduced morbidity and mortality due to colorectal cancer (CRC). As a general rule, however, next generation sequencing (NGS, either of gene panels or whole exomes) is relatively expensive and unaffordable for general clinical use. In resource-poor settings, performing NGS testing on an entire cohort of CRC patients, even if limited to those under 50 or 60 years of age, still places an enormous burden on limited resources. Although family history can be a good indicator for LS testing, identifying at-risk family members and offering cascade screening may not benefit many patients/probands without an obvious family history. This article presents a novel program called Modified Ascertainment and follow-up Program (MAP) with a scoring model for LS ascertainment and molecular screening by NGS with diagnosis confirmation of PV and cascade screening. The goal is to improve LS ascertainment in light of the growing burden of early-onset CRC, particularly in low- and middle-income countries. Through MAP, judiciously applied molecular genetics will improve identification of PV predisposing to LS and cascade screening.

The clinical features and management of Lynch syndrome-associated ovarian cancer

AIM

Lynch syndrome (LS) is one of the most common hereditary cancer syndromes, characterized by mutations in mismatch repair genes and autosomal dominant inheritance. Women with LS have an additional increased risk of gynecologic malignancies, including endometrial cancer (EC) and ovarian cancer (OC). Compared with EC, OC is relatively under investigation. This review thoroughly summarizes the current clinical evidence of surveillance, screening, and prevention strategies, and describes the molecular and clinical characteristics of LS-associated OC.

METHODS

An electronic search from databases of PubMed and Google Scholar was carried out using key words pertaining to Lynch syndrome and ovarian cancer. A review of the literatures including review articles, experimental, and observational studies published between 2000 and 2021 was conducted.

RESULTS

The lifetime risk of OC in women with LS of MLH1, MSH2, and MSH6 mutations is approximately 7%, with the median age at onset being 46 years, 10-15 years earlier than that in sporadic cases. Histologically, LS-associated OCs are primarily endometrioid (40%), high-grade (25%), and low-grade (11%) serous, or clear cell (6%) in nature. Eighty-five percent of patients are diagnosed at an early stage, presenting with a good prognosis at 84% 5-year survival. Optimal screening strategies for OC in LS are controversial; combined screening of patients' clinical and family history, immunohistochemical analysis, and microsatellite instability testing for mismatch repair deficiency have been proven efficient.

CONCLUSION

The clinical features were different between ovarian cancer in Lynch syndrome and sporadic cases. More research are needed for a greater understanding of the prevention and medical treatment of LS-associated OC.

Mismatch repair deficiency in early‐onset duodenal, ampullary, and pancreatic carcinomas is a strong indicator for a hereditary defect

Mismatch repair deficiency (dMMR) is a hallmark of Lynch syndrome (LS), but its prevalence in early‐onset (diagnosed under the age of 50 years) duodenal, ampullary, and pancreatic carcinomas (DC, AC, and PC, respectively) is largely unknown. We explored the prevalence of dMMR and the underlying molecular mechanisms in a retrospectively collected cohort of 90 early‐onset carcinomas of duodenal, ampullary, and pancreatic origin. dMMR was most prevalent in early‐onset DCs (47.8%); more than half of those were associated with hereditary cancer syndromes (LS or constitutional mismatch repair deficiency syndrome). All dMMR AC and PC were due to LS. Concordance of dMMR with underlying hereditary condition warrants ubiquitous dMMR testing in all early‐onset DC, AC, and PC.

Endometrial cancer in Lynch syndrome

Lynch syndrome (LS) is an autosomal dominant inherited disease caused by germline pathogenic variants (PVs) in mismatch repair (MMR) genes. LS-associated endometrial cancer (LS-EC) is the most common extraintestinal sentinel cancer caused by germline PVs in MMR genes, including MLH1, MSH2, MSH6 and PMS2. The clinicopathologic features of LS-EC include early age of onset, lower body mass index (BMI), endometrioid carcinoma and lower uterine segment involvement. There has been significant progress in screening, diagnosis, surveillance, prevention and treatment of LS-EC. Many studies support universal screening for LS among patients with EC. Screening mainly involves a combination of traditional clinical criteria and molecular techniques, including MMR-immunohistochemistry (MMR-IHC), microsatellite instability (MSI) testing, MLH1 promoter methylation testing and gene sequencing. The effectiveness of endometrial biopsy and transvaginal ultrasound (TVS) for clinical monitoring of asymptomatic women with LS are uncertain yet. Preventive strategies include hysterectomy and bilateral salpingo-oophorectomy (BSO) as well as chemoprophylaxis using exogenous progestin or aspirin. Recent research has revealed the benefits of immunotherapy for LS-EC. The NCCN guidelines recommend pembrolizumab and nivolumab for treating patients with advanced or recurrent microsatellite instability-high (MSI-H)/mismatch repair-deficient (dMMR) EC.

A 5-year retrospective review of skin adnexal tumours received at a tertiary dermatopathology service: Implications for linked genetic diagnoses

BACKGROUND

Skin adnexal tumours (SATs) comprise a diverse range of neoplasms, which are difficult to diagnose clinically. They present in paediatric and adult populations, and may be indicative of an underlying genetic syndrome. There is a lack of recent data on the presentation of these tumours in clinical practice in European populations.

OBJECTIVE

To characterise the clinical and pathological features of SATs received at a single tertiary centre over a 5-year period.

METHODS

A retrospective health record audit of SATs received at the Department of Cellular Pathology, Royal Victoria Infirmary, Newcastle upon Tyne Hospitals NHS Foundation Trust, during the period November 2012 to October 2017.

RESULTS

107144 skin cases were received during the audit period. 1615 cases of SATs from 1359 patients were included; 1570 (97.2%) were benign and 45 (2.8%) were malignant. Overall, the average age at presentation was 55 years (range 11 months - 97 years) and the male to female ratio was 0.77:1. Sweat gland and hair follicle SATs were most frequently excised; in adults the most frequent tumour was hidrocystoma, and in children, pilomatrixoma. Pre-biopsy diagnosis was correct 28% of the time. Benign SATs are often markers of an associated genetic condition, warranting improved discrimination of sporadic from genetically related SATs.

CONCLUSIONS

 SATs are difficult to diagnose clinically, and clinicopathological correlation may help enhance selection of genetically related SATs from sporadic cases. These data have implications for clinical and dermatopathological training provision, the development of reporting standards, and genetic assessment of selected patients.

Uptake of Genetic Testing Among Patients with Cancer At Risk for Lynch Syndrome in the National Health Interview Survey

Lynch syndrome is the most common inherited cancer syndrome that increases the risk of developing colorectal and endometrial cancer. Universal screening guidelines were first recommended by the Centers for Disease Control and Prevention (CDC) in 2009 and are updated annually by multiple societies. Therefore, one would expect genetic testing rates to increase over time. But testing remains underutilized among those with colorectal or endometrial cancer, even though early detection can improve prognosis and survival rates. In this study, we aimed to understand differences in genetic testing uptake among those with colorectal cancer or endometrial cancer from 2005, 2010, 2015, using data from the National Health Interview Survey (NHIS). We examined genetic testing uptake across cancer-type, age (≤50 or ≥51), sex, race, insurance, and education using a χ² statistical analysis. Despite an upward genetic testing trend in 2010, we found no significant differences in genetic testing uptake over time. In 2010, non-White individuals experienced the highest increase from 2005 in comparison with White individuals. However, genetic testing rates declined for both groups by 2015. Our findings show that genetic testing for colorectal cancer and endometrial cancer did not increase over a 10-year period in spite of guidelines that recommend testing. PREVENTION RELEVANCE: Genetic testing uptake for colorectal cancer and endometrial cancer has not increased over a 10-year period in spite of universal screening guidelines. More genetic testing education is needed at the provider and patient level to improve screening strategies for cancer patients who are most at risk for Lynch syndrome.

Predictive and Prognostic Value of Microsatellite Instability in Gynecologic Cancer (Endometrial and Ovarian)

Simple Summary

Endometrial cancers are the cancers most affected by microsatellite instability. This phenotype confers a demonstrated sensitivity to immunotherapy and in this sense is a major parameter to know in order to manage patients. Molecular biology, therefore, has an essential role in the better knowledge of these endometrial tumors. Moreover, the microsatellite instability phenotype is very poorly understood in ovarian cancer, yet it does exist. We therefore present here a review of the literature concerning microsatellite instability in gynecological cancers (endometrium and ovaries): its diagnosis, its clinical characteristics, and its therapeutic and prognostic impact.

Abstract

For endometrial cancer, a new classification is now available from ESMO, ESGO, and ESTRO based on clinical and molecular characteristics to determine adjuvant therapy. The contribution of molecular biology is major for this pathology mainly by the intermediary of deficient mismatch repair/microsatellite instability. Detection techniques for this phenotype have many peculiarities in gynecologic cancers (endometrial and ovarian) because it has been initially validated in colorectal cancer only. Endometrial cancer is the most common tumor with deficient mismatch repair, which is an important prognostic factor and a predictor of the benefit of adjuvant treatments. Concerning advanced stages, this phenotype is a theragnostic marker for using immunotherapy. Among ovarian cancer, microsatellite instability is less described in literature but exists, particularly in endometrioid type ovarian cancer. This review aims to provide an overview of the publications concerning deficient mismatch repair/microsatellite instability in endometrial and ovarian cancers, detection techniques, and clinical implications of these molecular characteristics.

Mismatch Repair Status Characterization in Oncologic Pathology: Taking Stock of the Real-World Possibilities

The mismatch repair (MMR) system has a key role in supporting the DNA polymerase proofreading function and in maintaining genome stability. Alterations in the MMR genes are driving events of tumorigenesis, tumor progression, and resistance to therapy. These genetic scars may occur in either hereditary or sporadic settings, with different frequencies across tumor types. Appropriate characterization of the MMR status is a crucial task in oncologic pathology because it allows for both the tailored clinical management of cancer patients and surveillance of individuals at risk. The currently available MMR testing methods have specific strengths and weaknesses, and their application across different tumor types would require a tailored approach. This article highlights the indications and challenges in MMR status assessment for molecular pathologists, focusing on the possible strategies to overcome analytical and pre-analytical issues.