Use of microsatellite instability and immunohistochemistry testing for the identification of individuals at risk for Lynch syndrome

Multivariable prognostic modelling to improve prediction of colorectal cancer recurrence: the PROSPeCT trial

OBJECTIVE

Improving prognostication to direct personalised therapy remains an unmet need. This study prospectively investigated promising CT, genetic, and immunohistochemical markers to improve the prediction of colorectal cancer recurrence.

MATERIAL AND METHODS

This multicentre trial (ISRCTN 95037515) recruited patients with primary colorectal cancer undergoing CT staging from 13 hospitals. Follow-up identified cancer recurrence and death. A baseline model for cancer recurrence at 3 years was developed from pre-specified clinicopathological variables (age, sex, tumour-node stage, tumour size, location, extramural venous invasion, and treatment). Then, CT perfusion (blood flow, blood volume, transit time and permeability), genetic (RAS, RAF, and DNA mismatch repair), and immunohistochemical markers of angiogenesis and hypoxia (CD105, vascular endothelial growth factor, glucose transporter protein, and hypoxia-inducible factor) were added to assess whether prediction improved over tumour-node staging alone as the main outcome measure.

RESULTS

Three hundred twenty-six of 448 participants formed the final cohort (226 male; mean 66 ± 10 years. 227 (70%) had ≥ T3 stage cancers; 151 (46%) were node-positive; 81 (25%) developed subsequent recurrence. The sensitivity and specificity of staging alone for recurrence were 0.56 [95% CI: 0.44, 0.67] and 0.58 [0.51, 0.64], respectively. The baseline clinicopathologic model improved specificity (0.74 [0.68, 0.79], with equivalent sensitivity of 0.57 [0.45, 0.68] for high vs medium/low-risk participants. The addition of prespecified CT perfusion, genetic, and immunohistochemical markers did not improve prediction over and above the clinicopathologic model (sensitivity, 0.58-0.68; specificity, 0.75-0.76).

CONCLUSION

A multivariable clinicopathological model outperformed staging in identifying patients at high risk of recurrence. Promising CT, genetic, and immunohistochemical markers investigated did not further improve prognostication in rigorous prospective evaluation.

CLINICAL RELEVANCE STATEMENT

A prognostic model based on clinicopathological variables including age, sex, tumour-node stage, size, location, and extramural venous invasion better identifies colorectal cancer patients at high risk of recurrence for neoadjuvant/adjuvant therapy than stage alone.

KEY POINTS

Identification of colorectal cancer patients at high risk of recurrence is an unmet need for treatment personalisation. This model for recurrence, incorporating many patient variables, had higher specificity than staging alone. Continued optimisation of risk stratification schema will help individualise treatment plans and follow-up schedules.

Current and Future Biomarkers in Esophagogastric Adenocarcinoma

PURPOSE

Biomarker-based therapies have shown improved patient outcomes across various cancer types. The purpose of this review to summarize our knowledge of current and future biomarkers in esophagogastric adenocarcinoma (EGA).

METHODS

In this publication, we will review current standard biomarkers in patients with upper GI cancers. We will also discuss novel biomarkers that are under investigations and their associated therapies that are currently in clinical trials.

RESULTS

EGAa are a group of heterogeneous diseases, both anatomically and molecularly. There are several established biomarkers (HER2, PD-L1, microsattelite instability or mismatch repair protein expression) that allow for individualized treatments for patients with these cancers. There are also several emerging biomarkers for EGA, some of which have clinically relevant associated therapies. Claudin 18.2 is the furthest along among these. Anti-claudin antibody, zolbetuximab, improved overall survival in biomarker select patients with advanced GEA in two phase 3 studies. Other novel biomarkers, such as FGFR2b and DKN01, are also in the process of validation, and treatments based on the presence of these biomarkers are currently in clinical studies.

CONCLUSION

Ongoing efforts to identify novel biomarkers in EGA have led to enhanced subclassification of upper GI cancers. These advances, coupled with the strategic application of targeted therapies and immunotherapy when appropriate, hold promise to further improve patients outcomes.

Molecular Approach to Colorectal Carcinoma: Current Evidence and Clinical Application

Colorectal carcinoma is one of the most common cancer types in men and women, responsible for both the third highest incidence of new cancer cases and the third highest cause of cancer deaths. In the last several decades, the molecular mechanisms surrounding colorectal carcinoma's tumorigenesis have become clearer through research, providing new avenues for diagnostic testing and novel approaches to therapeutics. Laboratories are tasked with providing the most current information to help guide clinical decisions. In this review, we summarize the current knowledge surrounding colorectal carcinoma tumorigenesis and highlight clinically relevant molecular testing.

Site-specific protein biomarkers in gastric cancer: a comprehensive review of novel biomarkers and clinical applications

INTRODUCTION

Gastric cancer (GC) is the fifth most common cancer and the fourth leading cause of cancer-related death worldwide, thus representing a significant global health burden. Early detection and monitoring of GC are essential to improve patient outcomes. While traditional cancer biomarkers such as carcinoembryonic antigen, carbohydrate antigen (CA) 19-9, and CA 72-4 are widely used, their limited sensitivity and specificity necessitate the exploration of alternative biomarkers.

AREAS COVERED

This review comprehensively analyzes the landscape of GC protein biomarkers identified from 2019 to 2022, with a focus on tissue, blood, urine, saliva, gastric juice, ascites, and exhaled breath as sample sources. We address the potential clinical applications of these biomarkers in early diagnosis, monitoring recurrence, and predicting survival and therapeutic response of GC patients.

EXPERT OPINION

The discovery of novel protein biomarkers holds great promise for improving the clinical management of GC. However, further validation in large, diverse cohorts is needed to establish the clinical utility of these biomarkers. Integrating these biomarkers with existing diagnostic and monitoring approaches will likely lead to improved personalized treatment plans and patient outcomes.

PMS2-associated Lynch syndrome: Past, present and future

Carriers of any pathogenic variant in one of the MMR genes (path_MMR carriers) were traditionally thought to be at comparable risk of developing a range of different malignancies, foremost colorectal cancer (CRC) and endometrial cancer. However, it is now widely accepted that their cancer risk and cancer spectrum range notably depending on which MMR gene is affected. Moreover, there is increasing evidence that the MMR gene affected also influences the molecular pathogenesis of Lynch syndrome CRC. Although substantial progress has been made over the past decade in understanding these differences, many questions remain unanswered, especially pertaining to path_PMS2 carriers. Recent findings show that, while the cancer risk is relatively low, PMS2-deficient CRCs tend to show more aggressive behaviour and have a worse prognosis than other MMR-deficient CRCs. This, together with lower intratumoral immune infiltration, suggests that PMS2-deficient CRCs might have more in common biologically with sporadic MMR-proficient CRCs than with other MMR-deficient CRCs. These findings could have important consequences for surveillance, chemoprevention and therapeutic strategies (e.g. vaccines). In this review we discuss the current knowledge, current (clinical) challenges and knowledge gaps that should be targeted by future studies.

Mismatch repair deficiency: The what, how and why it is important

The mismatch repair system is a major pathway that functions in the maintenance of genomic integrity. It is involved in mitotic and meiotic recombination, apoptosis, immunoglobulin gene rearrangement, somatic hypermutation, and other processes. Deficiencies in mismatch repair give rise to hypermutability and the phenomenon called microsatellite instability. Detection of deficient mismatch repair function or microsatellite instability is used diagnostically, predictively, and prognostically. Specifically, deficient mismatch repair function is used for screening of Lynch syndrome, determining patients who are likely to respond to immune checkpoint inhibition, and to contributes to an understanding of which cancer patients may pursue a more aggressive clinical course. Microsatellite instability can be evaluated directly by polymerase chain reaction (PCR) or indirectly by assessment of mismatch repair protein expression using immunohistochemistry (IHC), and mismatch repair function using next-generation sequencing assays which evaluates homopolymer indels. In this article, we provide a concise practical review on mismatch repair deficiency (MMR-d)/microsatellite instability (MSI), focusing on clinical testing, different testing methods, interpretation of findings, the predictive, and prognostic utility of MSI.

Molecular Approach to Colorectal Carcinoma: Current Evidence and Clinical Application

Colorectal carcinoma is one of the most common cancer types in men and women, responsible for both the third highest incidence of new cancer cases and the third highest cause of cancer deaths. In the last several decades, the molecular mechanisms surrounding colorectal carcinoma's tumorigenesis have become clearer through research, providing new avenues for diagnostic testing and novel approaches to therapeutics. Laboratories are tasked with providing the most current information to help guide clinical decisions. In this review, we summarize the current knowledge surrounding colorectal carcinoma tumorigenesis and highlight clinically relevant molecular testing.

Idylla MSI test as a new tool for microsatellite instability detection in sebaceous tumours and keratoacanthomas

AIM

Sebaceous tumours and keratoacanthomas can be associated with mismatch repair (MMR) deficiency and thus microsatellite instability (MSI). In such tumours, MSI phenotype could be an argument to search for an underlying Muir-Torre syndrome (MTS). MTS has been recognised as a variant of Lynch syndrome, characterised by a deficiency of the MMR proteins. In Lynch syndrome, the sensitivity and specificity of the techniques used to detect MSI is well described, which is not the case for skin tumours. In our hands, immunohistochemistry is a sensitive and specific method to detect MMR deficiency in those tumours. Contrasting with tumours of Lynch spectrum, sensitivity and specificity of molecular methods has not been extensively studied. This study aimed at evaluating two molecular methods to detect MSI phenotype in MTS associated tumours: a commonly used pentaplex PCR using Bethesda markers and the fully automated method using the Idylla MSI assay.

METHODS

A comparison between PCR, and Idylla was performed on 39 DNA extracted from cutaneous tumours. Immunohistochemistry was used as the gold standard to calculate sensitivity and specificity of both molecular techniques.

RESULTS

Concordant results were found in 32 cases (82%) with pentaplex PCR and in 36 cases (92%) with Idylla. The sensitivity of pentaplex PCR to detect MSI phenotype was 76% whereas Idylla sensitivity was 90%.

CONCLUSION

Idylla is more performant than PCR, for the detection of MSI in MTS-associated tumours and is a reliable additional technique to help detecting MTS in these tumours.

Is tumor testing efficiency for Lynch syndrome different in rectal and colon cancer?

BACKGROUND

Tumor testing utility in Lynch syndrome (LS) diagnosis is established.

AIMS

Analyze the differences between tumor testing efficiency in rectal (RC) and colon cancer (CC).

METHODS

We performed immunohistochemistry (IHC) for MisMatch Repair (MMR) proteins (IHC-MMR) and MicroSatellite Instability analysis (MSI) on 482 unselected primary tumors: 320 CCs and 162 RCs. Samples had proficient-IHC, deficient-IHC or borderline-IHC ("patchy" expression). MSI-H borderline-IHC tumors were considered as likely MMR-deficient. Germline testing was offered to MMR-deficient patients without BRAF mutation or MLH1 promoter hypermetilation (MLH1-Hy).

RESULTS

We identified 51/482 (10.6%) MMR-defective tumors. Multivariable analysis demonstrated a significant correlation between tumor testing results with histotype, lymph-node involvement and tumor location. In particular, RC showed a lower MMR-deficiency rate than CC (p<0.0001). Interestingly, MLH1 loss was detected in 0% RCs and 76.1% CCs, with 80% of them showing BRAF mutation/MLH1-Hy. A germline variant was detected in 12 out of 18 patients (mutation detection rate of 66.7%).

CONCLUSION

Tumor testing results showed molecular differences between CCs and RCs, in terms of MMR proteins expression, and presence of BRAF mutation/MLH1-Hy. MSH6 variants were the most frequent ones (50%). Although young age at diagnosis was associated with mutation detection (p = 0.045), 33.3% of LS patients were >50 years.

Gastrointestinal cancers: current biomarkers in esophageal and gastric adenocarcinoma

Esophageal and gastric adenocarcinomas are frequently diagnosed at an advanced stage and have a dismal prognosis. Even in patients with potentially curative cancer, nearly 50% will develop recurrent disease despite aggressive treatments. A number of biomarkers currently guide treatment decisions for patients with esophageal and gastric adenocarcinoma and include human epidermal growth factor receptor 2 (HER2) amplification, mismatch repair deficiency/microsatellite instability (dMMR/MSI-H) and program death-ligand 1 (PD-L1) expression. This review will focus on the function, testing and FDA-approved targeted therapies for HER2, dMMR/MSI-H and PD-L1. In addition, a number of novel targets in esophageal and gastric cancer are being studied in clinical trials. Neurotrophic-tropomyosin receptor kinase (NTRK), claudin-18 (CLDN18)/Rho GTPase activating protein 26 (ARHGAP26) gene fusion, fibroblast growth factor receptor (FGFR), lymphocyte-activation gene 3 (LAG3) and T cell immunoglobulin and mucin-domain containing-3 (TIM3) will be briefly reviewed. Despite several biomarkers used in the selection of treatment therapies, treatment outcomes remain poor. Future research efforts will focus on the identification of new biomarkers, moving existing biomarkers into earlier lines of therapy, and evaluating new combinations of existing biomarkers and therapies.

Quantitative evaluation of MSI testing using NGS detects the imperceptible microsatellite changed caused by MSH6 deficiency

Microsatellite instability (MSI) is an effective biomarker for diagnosing Lynch syndrome (LS) and predicting the responsiveness of cancer therapy. MSI testing is conventionally performed by capillary electrophoresis, and MSI status is judged by visual assessment of allele size change. Here, we attempted to develop a quantitative evaluation model of MSI using next-generation sequencing (NGS). Microsatellite markers were analyzed in tumor and non-tumor tissues of colorectal cancer patients by NGS after a single multiplex polymerase chain reaction amplification. The read counts corresponding to microsatellite loci lengths were calculated independently of mapping against a reference genome, and their distribution was digitized by weighted mean. Weighted mean differences between tumor and non-tumor samples with different MSI status were assessed, and cut-off values for each marker in the discovery cohort were determined. Each microsatellite maker was defined as unstable if the weighted mean difference was greater than the cut-off value. In the discovery cohort, the evaluation model demonstrated sensitivity and specificity of 100% for all markers. In the validation cohort, MSI status determined by the new model was consistent with the outcome of the conventional method in 29/30 cases (97%). The single inconsistent case was classified as low-frequency MSI by the conventional method but considered MSI-high by NGS. Genetic testing for mismatch repair genes revealed a pathogenic variant in MSH6 in the discordant case. We successfully developed a quantitative evaluation method for determining MSI status using NGS. This is a robust and sensitive method and could improve LS diagnosis.

The nonsense mutation MSH2 c.2152C>T shows a founder effect in Portuguese Lynch syndrome families

The mutational spectrum of the MMR genes is highly heterogeneous, but specific mutations are observed at high frequencies in well-defined populations or ethnic groups, due to founder effects. The MSH2 mutation c.2152C>T, p.(Gln718*), has occasionally been described in Lynch families worldwide, including in Portuguese Lynch syndrome families. During genetic testing for Lynch syndrome at the Portuguese Oncology Institutes of Porto and Lisbon, this mutation was identified in 28 seemingly unrelated families. In order to evaluate if this alteration is a founder mutation, haplotype analysis using microsatellite and SNP markers flanking the MSH2 gene was performed in the 28 probands and 87 family members. Additionally, the geographic origin of these families was evaluated and the age of the mutation estimated. Twelve different haplotypes were phased for 13 out of the 28 families and shared a conserved region of ∼3.6 Mb. Based on the mutation and recombination events observed in the microsatellite haplotypes and assuming a generation time of 25 years, the age estimate for the MSH2 mutation was 273 ± 64 years. The geographic origins of these families were mostly from the Northern region of Portugal. Concluding, these results suggest that the MSH2 c.2152C>T alteration is a founder mutation in Portugal with a relatively recent origin. Furthermore, its high proportion indicates that screening for this mutation as a first step, together with the previously reported Portuguese founder mutations, may be cost-effective in genetic testing of Lynch syndrome suspects of Portuguese ancestry.

DNA mismatch repair in cancer

Microsatellite instability (MSI) refers to the hypermutator phenotype secondary to frequent polymorphism in short repetitive DNA sequences and single nucleotide substitution, as consequence of DNA mismatch repair (MMR) deficiency. MSI secondary to germline mutation in DNA MMR proteins is the molecular fingerprint of Lynch syndrome (LS), while epigenetic inactivation of these genes is more commonly found in sporadic MSI tumors. MSI occurs at different frequencies across malignancies, although original methods to assess MSI or MMR deficiency have been developed mostly in LS related cancers. Here we will discuss the current methods to detect MSI/MMR deficiency with a focus of new tools which are emerging as highly sensitive detector for MSI across multiple tumor types. Due to high frequencies of non-synonymous mutations, the presence of frameshift-mutated neoantigens, which can trigger a more robust and long-lasting immune response and strong TIL infiltration with tumor eradication, MSI has emerged as an important predictor of sensitivity for immunotherapy-based strategies, as showed by the recent FDA's first histology agnostic-accelerated approval to immune checkpoint inhibitors for refractory, adult and pediatric, MMR deficient (dMMR) or MSI high (MSI-H) tumors. Moreover, it is known that MSI status may predict cancer response/resistance to certain chemotherapies. Here we will describe the complex interplay between the genetic and clinical-pathological features of MSI/dMMR tumors and the cancer immunotherapy, with a focus on the predictive and prognostic role of MMR status for immune checkpoint inhibitors (ICIs) and providing some suggestions on how to conceive better predictive markers for immunotherapy in the next future.

Screening for Lynch syndrome in young Saudi colorectal cancer patients using microsatellite instability testing and next generation sequencing

Individuals with Lynch syndrome (LS) have germline variants in DNA mismatch repair (MMR) genes that confer a greatly increased risk of colorectal cancer (CRC), often at a young age. Identification of these individuals has been shown to increase their survival through improved surveillance. We previously identified 33 high risk cases for LS in the Saudi population by screening for microsatellite instability (MSI) in the tumor DNA of 284 young CRC patients. The aim of the present study was to identify MMR gene variants in this cohort of patients. Peripheral blood DNA was obtained from 13 individuals who were at high risk of LS due to positive MSI status and young age (<60 years at diagnosis). Next generation sequencing, Sanger sequencing and Multiplex Ligation-dependent Probe Amplification were used to screen for germline variants in the MLH1, MSH2, MSH6 and PMS2 MMR genes. These were cross-referenced against several variant databases, including the International Society for Gastrointestinal Hereditary Tumors Incorporated database. Variants with pathogenic or likely pathogenic significance were identified in 8 of the 13 high risk cases (62%), comprising 4 in MLH1 and 4 in MSH2. All carriers had a positive family history for CRC or endometrial cancer. Next generation sequencing is an effective strategy for identifying young CRC patients who are at high risk of LS because of positive MSI status. We estimate that 7% of CRC patients aged <60 years in Saudi Arabia are due to LS, potentially involving around 50 new cases per year.

A Comprehensive Strategy for Accurate Mutation Detection of the Highly Homologous PMS2

Germline mutations in the DNA mismatch repair gene PMS2 underlie the cancer susceptibility syndrome, Lynch syndrome. However, accurate molecular testing of PMS2 is complicated by a large number of highly homologous sequences. To establish a comprehensive approach for mutation detection of PMS2, we have designed a strategy combining targeted capture next-generation sequencing (NGS), multiplex ligation-dependent probe amplification, and long-range PCR followed by NGS to simultaneously detect point mutations and copy number changes of PMS2. Exonic deletions (E2 to E9, E5 to E9, E8, E10, E14, and E1 to E15), duplications (E11 to E12), and a nonsense mutation, p.S22*, were identified. Traditional multiplex ligation-dependent probe amplification and Sanger sequencing approaches cannot differentiate the origin of the exonic deletions in the 3' region when PMS2 and PMS2CL share identical sequences as a result of gene conversion. Our approach allows unambiguous identification of mutations in the active gene with a straightforward long-range-PCR/NGS method. Breakpoint analysis of multiple samples revealed that recurrent exon 14 deletions are mediated by homologous Alu sequences. Our comprehensive approach provides a reliable tool for accurate molecular analysis of genes containing multiple copies of highly homologous sequences and should improve PMS2 molecular analysis for patients with Lynch syndrome.

Support Vector Machine Based on microRNA Expression Profiles to Predict Histological Origin of Ampullary Carcinoma: Case Report of a Patient Affected From Adenocarcinoma of the Papilla of Vater With Lynch Syndrome

Adenocarcinomas of Vater's papilla (PVAC) may originate from either the pancreatic duct or the intestinal epithelium. Conflicting data have been reported about the frequency of the 2 anatomical entities and their influence on patients' prognosis. To ascertain the anatomical origin of PVAC in a family member of a Lynch syndrome kindred, we searched for microRNA (miRNA) expression profiles on resected tumor specimens. The support vector machine was trained on our previous miRNAs expression data sets of pancreatic and colorectal tissue samples and used to classify the site of origin of the tumor in our patient. The support vector machine worked by contrasting the profiles of miRNAs in patients with pancreatic ductal and colorectal cancers to that of our patient, which was finally classified as pancreatic ductal adenocarcinoma accordingly to alterations of 55 miRNAs. The PVAC might be originated from ductal epithelium rather than from the intestinal mucosa of the papilla in the case at issue. Alteration of miR-548b-3p, miR-551a, miR-21, miR-92a, miR-let-7i, and miR-181a* emerged as potentially associated with cancer genetic susceptibility in PVAC.

Microsatellite instability and survival in gastric cancer: A systematic review and meta-analysis

Microsatellite instability (MSI) is associated with the prognosis in several cancers and is used for determination of the chemotherapy regimen in stage II colon cancer in the National Comprehensive Cancer Network guideline. However, the association between MSI and the prognosis of gastric cancer remains unclear. PubMed database was searched until January 2014 using MeSH terms and key words to identify the studies evaluating MSI and prognosis of gastric cancer and the references were manually searched. The main outcome was the overall survival rate and the subordinate outcome was the association between high-frequency MSI (MSI-H) and clinicopathological characteristics. Eight studies met the inclusion criteria and the majority of data were collected retrospectively. There were 1,976 patients, 431 of which were MSI-H patients, with a range of 11.68-33.82%. Four studies used the National Cancer Institute panel to define MSI-H, the other four had microsatellite markers ranging 2-11. Significant associations were found in three studies and the overall summary estimate was hazard ratio, 0.63 (95% confidence interval, 0.52-0.77), with no evidence of inter-study heterogeneity (I²=0.0%). MSI-H patients were identified to have a tendency to have less lymph node (LN) metastasis, superficial tumor invasion and to be intestinal type. In conclusion, MSI-H gastric cancers have an improved prognosis, accompanied with reduced risk of LN metastasis, tumor invasion and mortality.

Polymerase ɛ (POLE) mutations in endometrial cancer: clinical outcomes and implications for Lynch syndrome testing

BACKGROUND

DNA polymerase ɛ (POLE) exonuclease domain mutations characterize a subtype of endometrial cancer (EC) with a markedly increased somatic mutational burden. POLE-mutant tumors were described as a molecular subtype with improved progression-free survival by The Cancer Genome Atlas. In this study, the frequency, spectrum, prognostic significance, and potential clinical application of POLE mutations were investigated in patients with endometrioid EC.

METHODS

Polymerase chain reaction amplification and Sanger sequencing were used to test for POLE mutations in 544 tumors. Correlations between demographic, survival, clinicopathologic, and molecular features were investigated. Statistical tests were 2-sided.

RESULTS

Thirty POLE mutations (5.6%) were identified. Mutations were associated with younger age (<60 years; P=.001). POLE mutations were detected in tumors with microsatellite stability (MSS) and microsatellite instability (MSI) at similar frequencies (5.9% and 5.2%, respectively) and were most common in tumors with MSI that lacked mutL homolog 1 (MLH1) methylation (P<.001). There was no association with progression-free survival (hazard ratio, 0.22; P=.127).

CONCLUSIONS

The discovery that mutations occur with equal frequency in MSS and MSI tumors and are most frequent in MSI tumors lacking MLH1 methylation has implications for Lynch syndrome screening and mutation testing. The current results indicate that POLE mutations are associated with somatic mutation in DNA mismatch repair genes in a subset of tumors. The absence of an association between POLE mutation and progression-free survival indicates that POLE mutation status is unlikely to be a clinically useful prognostic marker. However, POLE testing in MSI ECs could serve as a marker of somatic disease origin. Therefore, POLE tumor testing may be a valuable exclusionary criterion for Lynch syndrome gene testing.

Lynch Syndrome in patients with clear cell and endometrioid cancers of the ovary

OBJECTIVE

Patients with Lynch Syndrome are at an increased risk for a variety of malignancies, including ovarian cancer. Ovarian cancers associated with Lynch Syndrome are predominantly clear cell or endometrioid in histology. Lynch Syndrome is characterized by germline mutations in mismatch repair (MMR) genes. The current study aims to assess the prevalence of loss of MMR expression in patients with endometrioid and clear cell ovarian carcinoma.

METHODS

A retrospective review identified 90 patients with endometrioid and/or clear cell carcinomas. Slides made from tumor tissue microarray blocks were evaluated using immunohistochemical stains with antibodies against MLH1, PMS2, MSH2, and MSH6. Statistical analysis was performed.

RESULTS

Seven of the 90 cases (7.8%) had loss of MMR expression. The mean age of patients with loss of MMR expression (47 years) was significantly younger than those with retained MMR expression (p=0.014). Loss of MMR expression was present in 20% of patients under the age of 53 with clear cell or endometrioid cancers. Genetic studies found that 3 of the 5 patients with loss of MMR expression carried mutations consistent with Lynch Syndrome; acquired hypermethylation of MLH1 was noted in one patient. Six of 7 patients (86%) whose tumors lacked MMR expression had synchronous or metachronous primary malignancies, a significantly greater prevalence than those with retained MMR expression (p<0.001).

CONCLUSION

Patients under the age of 53 with clear cell or endometrioid ovarian carcinomas are at a clinically significant risk for loss of MMR expression and Lynch Syndrome; routine screening with immunohistochemical staining should be considered.

The mechanism of mismatch repair and the functional analysis of mismatch repair defects in Lynch syndrome

The majority of Lynch syndrome (LS), also known as hereditary non-polyposis colorectal cancer (HNPCC), has been linked to heterozygous defects in DNA mismatch repair (MMR). MMR is a highly conserved pathway that recognizes and repairs polymerase misincorporation errors and nucleotide damage as well as functioning as a damage sensor that signals apoptosis. Loss-of-heterozygosity (LOH) that retains the mutant MMR allele and epigenetic silencing of MMR genes are associated with an increased mutation rate that drives carcinogenesis as well as microsatellite instability that is a hallmark of LS/HNPCC. Understanding the biophysical functions of the MMR components is crucial to elucidating the role of MMR in human tumorigenesis and determining the pathogenetic consequences of patients that present in the clinic with an uncharacterized variant of the MMR genes. We summarize the historical association between LS/HNPCC and MMR, discuss the mechanism of the MMR and finally examine the functional analysis of MMR defects found in LS/HNPCC patients and their relationship with the severity of the disease.

Association between IHC and MSI testing to identify mismatch repair-deficient patients with ovarian cancer

OBJECTIVE

In epithelial ovarian cancer, concordance between results of microsatellite instability (MSI) and immunohistochemical (IHC) testing has not been demonstrated. This study evaluated the association of MSI-high (MSI-H) status with loss of expression (LoE) of mismatch repair (MMR) proteins on IHC and assessed for potential factors affecting the strength of the association.

METHODS

Tumor specimens from three population-based studies of epithelial ovarian cancer were stained for MMR proteins through manual or automated methods, and results were interpreted by one of two pathologists. Tumor and germline DNA was extracted and MSI testing performed. Multivariable logistic regression models were fitted to predict loss of IHC expression based on MSI status after adjusting for staining method and reading pathologist.

RESULTS

Of 834 cases, 564 (67.6%) were concordant; 41 were classified as MSI-H with LoE and 523 as microsatellite stable (MSS) with no LoE. Of the 270 discordant cases, 83 were MSI-H with no LoE and 187 were MSS with LoE. Both IHC staining method and reading pathologist were strongly associated with discordant results.

CONCLUSIONS

Lack of concordance in the current study may be related to inconsistencies in IHC testing methods and interpretation. Results support the need for validation studies before routine screening of ovarian tumors is implemented in clinical practice for the purpose of identifying Lynch syndrome.

Molecular profiling in colorectal cancer: current state of play and future directions

SUMMARY In the era of molecular scientific discovery, there is a continuing gap between our growing scientific knowledge and its utility at the bedside. This phenomenon probably occurs more frequently in colorectal cancer than in other cancer streams, with thousands of scientific studies having produced only a handful of molecular interventions. This review examines our current practices of molecular profiling in colorectal cancer and the scientific research that may impact on this area in the future.

Molecular alterations and biomarkers in colorectal cancer

The promise of precision medicine is now a clinical reality. Advances in our understanding of the molecular genetics of colorectal cancer (CRC) are leading to the development of a variety of biomarkers that are being used as early detection markers, prognostic markers, and markers for predicting treatment responses. This is no more evident than in the recent advances in testing CRCs for specific molecular alterations in order to guide treatment with the monoclonal antibody therapies cetuximab and panitumumab, which target the epidermal growth factor receptor. In this review, we update a prior review published in 2010 and describe our current understanding of the molecular pathogenesis of CRC and how these alterations relate to emerging biomarkers for early detection and risk stratification (diagnostic markers), prognosis (prognostic markers), and the prediction of treatment responses (predictive markers).

Relationship between PTEN, DNA mismatch repair, and tumor histotype in endometrial carcinoma: retained positive expression of PTEN preferentially identifies sporadic non-endometrioid carcinomas

Loss of PTEN (phosphatase and tensin homolog) expression and microsatellite instability are two of the more common molecular alterations in endometrial carcinoma. From the published literature, it is controversial as to whether there is a relationship between these different molecular mechanisms. Therefore, a cohort of 187 pure endometrioid and non-endometrioid endometrial carcinomas, carefully characterized as to clinical and pathological features, was examined for PTEN sequence abnormalities and the immunohistochemical expression of PTEN and the DNA mismatch repair proteins MLH1, MSH2, MSH6, and PMS2. MLH1 methylation analysis was performed when tumors had loss of MLH1 protein. Mismatch repair protein loss was more frequent in endometrioid carcinomas compared with non-endometrioid carcinomas, a difference primarily attributable to the presence of MLH1 methylation in a greater proportion of endometrioid tumors. Among the non-endometrioid group, mixed endometrioid/non-endometrioid carcinomas were the histotype that most commonly had loss of a mismatch repair protein. In endometrioid tumors, the frequency of PTEN loss measured by immunohistochemistry and mutation did not differ significantly between the mismatch repair protein intact or mismatch repair protein loss groups, suggesting that PTEN loss is independent of mismatch protein repair status in this group. However, in non-endometrioid carcinomas, both intact positive PTEN immunohistochemical expression and PTEN wild type were highly associated with retained positive expression of mismatch repair proteins in the tumor. Relevant to screening endometrial cancers for Lynch Syndrome, an initial PTEN immunohistochemistry determination may be able to replace the use of four mismatch repair immunohistochemical markers in 63% of patients with non-endometrioid endometrial carcinoma. Therefore, PTEN immunohistochemistry, in combination with tumor histotype, is a useful adjunct in the clinical evaluation of endometrial carcinomas for Lynch Syndrome.

Application of Immunohistochemistry and Molecular Diagnostics to Clinically Relevant Problems in Endometrial Cancer Bojana Djordjevic, Shannon Westin, Russell R. Broaddus

A number of different clinical scenarios are presented in which lab-based analyses beyond the usual diagnosis based on light microscopic examination of H&E stained slides - immunohistochemistry and PCR-based assays such as sequencing, mutation testing, microsatellite instability analysis, and determination of MLH1 methylation - are most helpful for guiding diagnosis and treatment of endometrial cancer. The central goal of this information is to provide a practical guide of key current and emerging issues in diagnostic endometrial cancer pathology that require the use of ancillary laboratory techniques, such as immunohistochemistry and molecular testing. The authors present the common diagnostic problems in endometrial carcinoma pathology, types of endometrial carcinoma, description of tissue testing and markers, pathological features, and targeted therapy.

Lynch syndrome in a predominantly Afrocentric population: a clinicopathological and genetic study

BACKGROUND

We investigated the prevalence of Lynch syndrome as a hereditary cause of colon cancer in the young Jamaican colorectal cancer (CRC) population.

METHODS

We identified patients aged 40 years or younger in whom primary CRC was diagnosed at the University Hospital of the West Indies from January 2004 to December 2008. We reviewed the medical records and hematoxylin and eosin (H&E)-stained histopathology slides. Tumour blocks were tested for microsatellite instability (MSI). Patients with MSI-high phenotype (MSI-H) tumours had genetic counselling, after which genomic DNA was extracted from peripheral blood to test for MLH1 and MSH2 germline mutations. Patients also had pedigree mapping.

RESULTS

There were 25 patients with CRC aged 40 years or younger with no history of hereditary colon cancer syndrome. The patients' mean age was 33 (range 21-40) years. Histopathologic review confirmed CRC in all patients; 8 of 25 (32%) showed morphologic features suggestive of MSI. We detected MSI-H in 5 of 23 (22%) tumour blocks tested. Review with H&E staining correctly identified 80% of cases positive for MSI-H. The false-positive rate and positive predictive value on H&E review was 50%. The negative predictive value of histomorphologic H&E review was 94%. Three patients were available for and had mutational analysis of DNA mismatch repair genes; 2 were positive for mutations in keeping with Lynch syndrome and 1 had MLH1 alterations of uncertain significance. All 3 met the Amsterdam criteria for hereditary nonpolyposis CRC.

CONCLUSION

Thirteen percent of the population had mutations in keeping with Lynch syndrome. This prevalence is similar to that reported for white populations.

High incidence of microsatellite instability and loss of heterozygosity in three loci in breast cancer patients receiving chemotherapy: a prospective study

Background

The aim of the study was to evaluate potential chemotherapy-induced microsatellite instability, loss of heterozygosity, loss of expression in mismatch repair proteins and associations with clinical findings in breast cancer patients, especially resistance to chemotherapy and/or development of other tumors in the four years following chemotherapy treatment.

Methods

A comprehensive study of chemotherapy-related effects with a follow-up period of 48 months post treatment was conducted. A total of 369 peripheral blood samples were collected from 123 de novo breast cancer patients. Microsatellite instability and loss of heterozygosity in five commonly used marker loci (including Tp53-Alu of the tumor suppressor gene TP53) were analyzed in blood samples. Sampling was conducted on three occasions; 4–5 weeks prior to the first chemotherapy session (pre-treatment), to serve as a baseline, followed by two consecutive draws at 12 weeks intervals from the first collection. Mismatch repair protein expression was evaluated in cancer tissues using immunohistochemistry for three mismatch-repair related proteins.

Results

A total of 70.7% of the patients showed microsatellite instability for at least one locus, including 18.6% marked as high-positive and 52.1% as low-positive; 35.8% showed loss of heterozygosity in addition to microsatellite instability, while 29.3% exhibited microsatellite stability. The following incidence rates for microsatellite instability and loss of heterozygosity were detected: 39.1% positive for Tp53-Alu, 31.1% for locus Mfd41, and 25.3% for locus Mfd28. A higher occurrence of loss of heterozygosity was noted with alleles 399 and 404 of Tp53-Alu. The mismatch repair protein expression analysis showed that the chemotherapy caused a loss of 29.3% in hMLH1 expression, and 18.7% and 25.2% loss in hMSH2 and P53 expression, respectively. A strong correlation between low or deficient hMSH2 protein expression and occurrence of mismatch repair/loss of heterozygosity events in Mfd41, Tp53-Alu, and Mfd28 was evident. A significant association between mismatch repair/loss of heterozygosity and incidence of secondary tumors was also established.

Conclusion

Our results suggest that microsatellite instability, loss of heterozygosity, and deficiency in mismatch repair may serve as early prognostic factors for potential chemotherapy-related side effects in breast cancer patients.

The germline MLH1 K618A variant and susceptibility to Lynch syndrome-associated tumors

Missense variants discovered during sequencing of cancer susceptibility genes can be problematic for clinical interpretation. MLH1 K618A, which results from a 2-bp alteration (AAG→GCG) leading to a substitution of lysine to alanine in codon 618, has variously been interpreted as a pathogenic mutation, a variant of unknown significance, and a benign polymorphism. We evaluated the role of MLH1 K618A in predisposition to cancer by genotyping 1512 control subjects to assess its frequency in the general population. We also reviewed the literature concerning MLH1 K618A in families with colorectal cancer. The measured allele frequency of the K618A variant was 0.40%, which is remarkably close to the 0.44% summarized from 2491 control subjects in the literature. K618A was over-represented in families with suspected Lynch syndrome. In 1366 families, the allele frequency was 0.88% (OR = 2.1, 95% CI = 1.3 to 3.5; P = 0.006). In studies of sporadic cancers of the type associated with Lynch syndrome, K618A was over-represented in 1742 cases (allele frequency of 0.83) (OR = 2.0, 95% CI = 1.2 to 3.2; P = 0.008). We conclude that MLH1 K618A is not a fully penetrant Lynch syndrome mutation, although it is not without effect, appearing to increase the risk of Lynch syndrome-associated tumors approximately twofold. Our systematic assessment approach may be useful for variants in other genes.

Germline mutation analysis of MLH1 and MSH2 in Malaysian Lynch syndrome patients

AIM: To investigate the protein expression profile of mismatch repair (MMR) genes in suspected cases of Lynch syndrome and to characterize the associated germline mutations.

METHODS: Immunohistochemical analysis of tumor samples was performed to determine the protein expression profile of MMR protein. Germline mutation screening was carried out on peripheral blood samples. The entire exon regions of MLH1 and MSH2 genes were amplified by polymerase chain reaction, screened by denaturing high performance liquid chromatography (dHPLC) and analyzed by DNA sequencing to characterize the germline mutations.

RESULTS: Three out of 34 tissue samples (8.8%) and four out of 34 tissue samples (11.8%) showed loss of nuclear staining by immunohistochemistry, indicating the absence of MLH1 and MSH2 protein expression in carcinoma cells, respectively. dHPLC analysis followed by DNA sequencing showed these samples to have germline mutations of MSH2 gene. However, no deleterious mutations were identified in any of the 19 exons or coding regions of MLH1 gene, but we were able to identify MLH1 promoter polymorphism, -93G > A (rs1800734), in 21 out of 34 patients (61.8%). We identified one novel mutation, transversion mutation c.2005G > C, which resulted in a missense mutation (Gly669Arg), a transversion mutation in exon 1, c.142G > T, which resulted in a nonsense mutation (Glu48Stop) and splice-site mutation, c.2006-6T > C, which was adjacent to exon 13 of MSH2 gene.

CONCLUSION: Germline mutations were identified in four Malaysian Lynch syndrome patients. Immunohistochemical analysis of tumor tissue proved to be a good pre-screening test before proceeding to germline mutation analysis of DNA MMR genes.

Relevance, pathogenesis, and testing algorithm for mismatch repair-defective colorectal carcinomas: a report of the association for molecular pathology

Loss-of-function defects in DNA mismatch repair (MMR), which manifest as high levels of microsatellite instability (MSI), occur in approximately 15% of all colorectal carcinomas (CRCs). This molecular subset of CRC characterizes patients with better stage-specific prognoses who experience no benefit from 5-fluorouracil chemotherapy. Most MMR-deficient (dMMR) CRCs are sporadic, but 15% to 20% are due to inherited predisposition (Lynch syndrome). High penetrance of CRCs in germline MMR gene mutation carriers emphasizes the importance of accurate diagnosis of Lynch syndrome carriers. Family-based (Amsterdam), patient/family-based (Bethesda), morphology-based, microsatellite-based, and IHC-based screening criteria do not individually detect all germline mutation carriers. These limitations support the use of multiple concurrent tests and the screening of all patients with newly diagnosed CRC. This approach is resource intensive but would increase detection of inherited and de novo germline mutations to guide family screening. Although CRC prognosis and prediction of 5-fluorouracil response are similar in both the Lynch and sporadic dMMR subgroups, these subgroups differ significantly with regard to the implications for family members. We recommend that new CRCs should be classified into sporadic MMR-proficient, sporadic dMMR, or Lynch dMMR subgroups. The concurrent use of MSI testing, MMR protein IHC, and BRAF c.1799T>A mutation analysis would detect almost all dMMR CRCs, would classify 94% of all new CRCs into these MMR subgroups, and would guide secondary molecular testing of the remainder.

Expanding DNA diagnostic panel testing: is more better?

During the last 25 years, a small number of meaningful DNA-based diagnostic tests have been available to aid in the diagnosis and subsequent treatment of heritable disorders. These tests have targeted a limited number of genes and are often ordered in serial testing strategies in which results from one preliminary test dictate the subsequent test orders. This approach can be both time and resource intensive when a patient requires several genes to be sequenced. Recently, there has been much discussion regarding how 'massively parallel' or 'next-generation' DNA sequencing will impact clinical care. While the technology promises to reduce the cost of sequencing an entire human genome to less than US$1000, one must question the diagnostic utility of complete genome sequencing for routine clinical testing, given the many interpretive challenges posed by this approach. At present, it appears next-generation DNA sequencing may provide the greatest benefit to routine clinical testing by enabling comprehensive multigene panel sequencing. This should provide an advantage over traditional Sanger-based sequencing strategies while limiting the total test output to sets to genes with known diagnostic value. This article will discuss the current and near future state of clinical testing approaches and explore what challenges must be addressed in order to extract diagnostic value from whole-exome sequencing and whole-genome sequencing, using hereditary colon cancer as an example.

Identification of cancer patients with Lynch syndrome: clinically significant discordances and problems in tissue-based mismatch repair testing

Tissue-based microsatellite instability (MSI) analysis and immunohistochemistry for DNA mismatch repair proteins are accepted screening tools to evaluate patients with cancer for Lynch syndrome. These laboratory analyses are thus important tools in cancer prevention. Quality assurance review was conducted to identify test discordances and problems. These results were then analyzed in conjunction with genetic testing outcomes. Six hundred and forty-six consecutive tumors from 2002 to 2010 were examined. MSI-low tumors were excluded so that 591 tumors comprised the final analyses. Discordance was defined as a discrepancy between immunohistochemical and MSI analysis. Problem was defined as indeterminate or questionable immunohistochemical or MSI results. All results and clinical and family histories were centrally reviewed by two pathologists and one genetics counselor. Discordances and problems were identified in 23 of 591 (3.9%) of the tumors. Twelve of 102 MSI-high carcinomas (11.8%) and one of 489 microsatellite stable tumors had discordant immunohistochemistry. Of these 13 tumors, 11 were from patients who had personal and/or family cancer histories concerning for a germline mismatch repair gene mutation. In addition to discordances, 10 tumors with problematic immunohistochemical profiles were identified. Accurate evaluation of MSI was possible in all tumors. In summary, concordance between immunohistochemistry and MSI was high, particularly for tumors that are microsatellite stable. Greater frequency of test discordance was identified in the tumors that were MSI-high. Thus, a major consequence of the use of immunohistochemistry by itself as a screen is the failure to identify colorectal and endometrial cancer patients who likely have Lynch syndrome.

Implementing screening for Lynch syndrome among patients with newly diagnosed colorectal cancer: summary of a public health/clinical collaborative meeting

Lynch syndrome is the most common cause of inherited colorectal cancer, accounting for approximately 3% of all colorectal cancer cases in the United States. In 2009, an evidence-based review process conducted by the independent Evaluation of Genomic Applications in Practice and Prevention Working Group resulted in a recommendation to offer genetic testing for Lynch syndrome to all individuals with newly diagnosed colorectal cancer, with the intent of reducing morbidity and mortality in family members. To explore issues surrounding implementation of this recommendation, the Centers for Disease Control and Prevention convened a multidisciplinary working group meeting in September 2010. This article reviews background information regarding screening for Lynch syndrome and summarizes existing clinical paradigms, potential implementation strategies, and conclusions which emerged from the meeting. It was recognized that widespread implementation will present substantial challenges, and additional data from pilot studies will be needed. However, evidence of feasibility and population health benefits and the advantages of considering a public health approach were acknowledged. Lynch syndrome can potentially serve as a model to facilitate the development and implementation of population-level programs for evidence-based genomic medicine applications involving follow-up testing of at-risk relatives. Such endeavors will require multilevel and multidisciplinary approaches building on collaborative public health and clinical partnerships.

Pancreatic cancer and a novel MSH2 germline alteration

OBJECTIVE

The objective of this study was to describe a novel MSH2 missense alteration cosegregating with pancreatic cancer.

METHODS

The method used was an observational study of a kindred in which a novel MSH2 missense alteration was identified.

RESULTS

We report a family in which a MSH2 P349L missense alteration is cosegregating with pancreatic cancers among 3 nonsmoking first-degree relatives. Lynch syndrome-related tumors from individuals carrying this alteration consistently showed loss of immunohistochemical expression of MSH2, and in silico analyses support the interpretation of this DNA alteration as likely pathogenic.

CONCLUSIONS

The MSH2 P349L may increase the risk for pancreatic cancer beyond the usual mutations in DNA mismatch repair genes; however, studies of additional families with the identical missense alteration are needed to confirm this initial impression.

Screening for Lynch syndrome in colorectal cancer: are we doing enough?

PURPOSE

The purpose of this study was to assess the efficacy of screening for the detection of Lynch syndrome (LS) in an unselected population undergoing surgery for a colorectal cancer.

METHODS

A total of 1,040 patients were prospectively included between 2005 and 2009. LS screening modalities included the Bethesda criteria, immunochemistry (IHC) for MLH1, MSH2, and MSH6, and microsatellite instability (MSI) by using pentaplex markers. Promoter methylation was assessed in tumors with a loss of MLH1 expression. Gene sequencing was offered to patients with abnormal IHC or MSI status without promoter methylation.

RESULTS

A total of 105 patients had an abnormal result: 102 (9.8%) exhibited a loss of protein on IHC and 98 (9.4%) had MSI. A discordant result was observed in 10 patients with eventual proven LS in 6 patients. Loss of MLH1 (n = 64) was due to promoter methylation in 43 patients (67.2%). Overall, of 62 patients with an abnormal result, 38 had genetic sequencing leading to 25 (65.8%) identified with a germ-line mutation. Loss of MSH2 on IHC was associated with a mutation in 78.3% (18 of 23) of cases. Among the 62 patients with abnormal results, 23 (37.1%) did not meet the Bethesda criteria.

CONCLUSIONS

Strict application of the Bethesda criteria does not lead to identification of all patients with LS. IHC and MSI testing are complementary methods and should be used in association to identify potential LS patients.

miRNA expression in colon polyps provides evidence for a multihit model of colon cancer

Changes in miRNA expression are a common feature in colon cancer. Those changes occurring in the transition from normal to adenoma and from adenoma to carcinoma, however, have not been well defined. Additionally, miRNA changes among tumor subgroups of colon cancer have also not been adequately evaluated. In this study, we examined the global miRNA expression in 315 samples that included 52 normal colonic mucosa, 41 tubulovillous adenomas, 158 adenocarcinomas with proficient DNA mismatch repair (pMMR) selected for stage and age of onset, and 64 adenocarcinomas with defective DNA mismatch repair (dMMR) selected for sporadic (n = 53) and inherited colon cancer (n = 11). Sporadic dMMR tumors all had MLH1 inactivation due to promoter hypermethylation. Unsupervised PCA and cluster analysis demonstrated that normal colon tissue, adenomas, pMMR carcinomas and dMMR carcinomas were all clearly discernable. The majority of miRNAs that were differentially expressed between normal and polyp were also differentially expressed with a similar magnitude in the comparison of normal to both the pMMR and dMMR tumor groups, suggesting a stepwise progression for transformation from normal colon to carcinoma. Among the miRNAs demonstrating the largest fold up- or down-regulated changes (≥4), four novel (miR-31, miR-1, miR-9 and miR-99a) and two previously reported (miR-137 and miR-135b) miRNAs were identified in the normal/adenoma comparison. All but one of these (miR-99a) demonstrated similar expression differences in the two normal/carcinoma comparisons, suggesting that these early tumor changes are important in both the pMMR- and dMMR-derived cancers. The comparison between pMMR and dMMR tumors identified four miRNAs (miR-31, miR-552, miR-592 and miR-224) with statistically significant expression differences (≥2-fold change).

Integrated analysis of unclassified variants in mismatch repair genes

PURPOSE

Lynch syndrome is a genetic disease that predisposes to colorectal tumors, caused by mutation in mismatch repair genes. The use of genetic tests to identify mutation carriers does not always give perfectly clear results, as happens when an unclassified variant is found. This study aimed to define the pathogenic role of 35 variants present in MSH2, MLH1, MSH6, and PMS2 genes identified in our 15-year case study.

METHODS

We collected clinical and molecular data of all carriers, and then we analyzed the variants pathogenic role with web tools and molecular analyses. Using a Bayesian approach, we derived a posterior probability of pathogenicity and classified each variant according to a standardized five-class system.

RESULTS

The MSH2 p.Pro349Arg, p.Met688Arg, the MLH1 p.Gly67Arg, p.Thr82Ala, p.Lys618Ala, the MSH6 p.Ala1236Pro, and the PMS2 p.Arg20Gln were classified as pathogenic, and the MSH2 p.Cys697Arg and the PMS2 p.Ser46Ile were classified as likely pathogenic. Seven variants were likely nonpathogenic, 3 were nonpathogenic, and 16 remained uncertain.

CONCLUSION

Quantitative assessment of several parameters and their integration in a multifactorial likelihood model is the method of choice for classifying the variants. As such classifications can be associated with surveillance and testing recommendations, the results and the method developed in our study can be useful for helping laboratory geneticists in evaluation of genetic tests and clinicians in the management of carriers.

Lower gastrointestinal tract cancer predisposition syndromes

Although inherited predisposition to colorectal cancer (CRC) has been suspected for more than 100 years, definitive proof of Mendelian syndromes had to await maturation of molecular genetic technologies. Since the l980s, the genetics of several clinically distinct entities has been revealed. Five disorders that share a hereditary predisposition to CRC are reviewed in this article.

How to manage a patient with multiple adenomatous polyps

Adenomatous polyps are found on screening colonoscopy in 22.5% to 58.2% of the adult population and therefore represent a common problem. Patients with multiple adenomatous polyps are of unique interest because a proportion of these patients have an inheritable form of colorectal cancer. This article discusses the history and clinical features, genetic testing, surveillance, and treatments for the condition.

Atypical identification of Lynch syndrome by immunohistochemistry and microsatellite instability analysis on jejunal adenocarcinoma

As we learn more about the etiology and cancer risks associated with Lynch syndrome (LS), the phenotypic spectrum of this condition and its genotype-phenotype correlations are being elucidated. We report a patient with past history of multiple cancers including colon and kidney cancer, and recently diagnosed with jejunal adenocarcinoma. The patient had microsatellite instability and immunohistochemistry (MSI/IHC) testing performed on his small bowel cancer in order to evaluate his risk for LS. The MSI/IHC results on his tumor tissue were reported as abnormal and subsequent blood draw revealed the presence of a germline MSH6 mismatch repair gene mutation. This case highlights the phenotypic variability of LS and complications it may present in evaluation for diagnosis and appropriate surveillance and management recommendations. To our knowledge, this is the first report of MSI/IHC being done on small bowel cancer to evaluate for this condition and subsequently confirmed via molecular analysis.

In Lynch syndrome adenomas, loss of mismatch repair proteins is related to an enhanced lymphocytic response

AIMS

Lynch syndrome-associated tumours are characterized by the presence of an increased number of tumour-infiltrating lymphocytes. This enhanced lymphocytic response may be elicited by genetically altered proteins that may arise as a result of a defective DNA mismatch repair system. The aim was to investigate this hypothesis by correlating loss of mismatch repair proteins and infiltration of lymphocytes in Lynch syndrome-associated adenomas and hyperplastic polyps.

METHODS AND RESULTS

Mismatch repair protein expression and the number of tumour-infiltrating lymphocytes were assessed in Lynch syndrome (41 adenomas and nine hyperplastic polyps) and in familial colorectal cancer (nine adenomas and one hyperplastic polyp). Nineteen sporadic adenomas were included as a control group. Twenty of 32 (63%) adenomas with loss of mismatch repair protein expression showed an increase in tumour-infiltrating lymphocytes. Eight adenomas (8/32; 25%) displayed many tumour-infiltrating lymphocytes, whereas most adenomas (12/32; 38%) showed a minor increase. In adenomas with mismatch repair protein expression, both sporadic and Lynch syndrome associated, not one showed an increased number of tumour-infiltrating lymphocytes. Hyperplastic polyps in Lynch syndrome patients showed neither loss of mismatch repair expression nor an increase in tumour-infiltrating lymphocytes.

CONCLUSIONS

There is a correlation between the loss of mismatch repair proteins and the infiltration of lymphocytes in Lynch syndrome-associated adenomas.