Semiquantitative assessment of immunohistochemistry for mismatch repair proteins in Lynch syndrome

Case report: Undifferentiated sarcoma with multiple tumors involved in Lynch syndrome: Unexpected favorable outcome to sintilimab combined with chemotherapy

Background

Patients with Lynch syndrome are at an increased risk of developing simultaneous or metachronous tumors, while sarcomas have been occasionally reported. Sarcomas are generally not considered part of the common Lynch syndrome tumor spectrum. However, more and more studies and case reports suggested that sarcoma could be a rare clinical manifestation of Lynch syndrome, leading to new treatment strategies for sarcoma.

Case summary

We report the case of a 74-year-old male patient with Lynch syndrome who had rectal mucinous adenocarcinoma and prostate adenocarcinoma and then developed undifferentiated sarcoma of the left neck two years later. Mismatch repair deficiency (dMMR) was confirmed by immunohistochemical staining for the mismatch repair proteins MSH2, MSH6, MLH1 and PMS2. The result of polymerase chain reaction (PCR) microsatellite instability (MSI) testing of sarcoma showed high-level microsatellite instability (MSI-H). Additionally, a pathogenic germline mutation in MSH2 (c.2459-12A>G) was detected by next-generation sequencing (NGS). Taking into account HE morphology, immunohistochemical phenotype, MSI status, NGS result, medical history and germline MSH2 gene mutation, the pathological diagnosis of left neck biopsy tissue was Lynch syndrome related undifferentiated sarcoma with epithelioid morphology. The patient has been receiving immunotherapy (sintilimab) combined with chemotherapy (tegafur, gimeracil and oteracil potassium capsules) and currently has stable disease. We also reviewed the literature to understand the association between sarcoma and Lynch syndrome.

Conclusion

Sarcoma may now be considered a rare clinical manifestation of Lynch syndrome. Attention and awareness about the association between Lynch syndrome and sarcoma need to be increased. Therefore, timely detection of MMR proteins and validation at the gene level for suspicious patients are the keys to avoiding missed or delayed diagnosis and to identifying patients suited for immunotherapy, which may also help to provide appropriate genetic counseling and follow-up management for patients.

An effective algorithm to detect the possibility of being MSI phenotype in endometrial cancer given the BMI status and histological subtype: a statistical study

Purpose

In endometrial cancer, the incidence of mutations in mismatch repair genes (MMR) is estimated at 17–30%. Patients with alterations at this level (MSI) are known to have different clinical and anatomopathological characteristics than those without this genetic alteration (MSS). In this study, we aim to identify the MSI phenotype in patients who underwent hysterectomy for endometrial cancer. We assessed the correlation of this phenotype with anatomoclinical parameters such as obesity and histological subtype.

Methods/patients

Clinical and anatomopathological data were collected from 147 patients diagnosed with endometrial cancer and an immunohistochemical study of MMR system proteins was performed. PMS2 and MSH6 proteins were evaluated as primary screening and subsequent evaluation of MLH1 and MSH6, respectively, if the former were negative. Statistical association between the anatomopathological data and the immunohistochemical result was analyzed.

Results and conclusions

22.4% of our patients were MSI phenotype. We obtained statistically significant differences by multivariate analysis between endometrioid subtype and higher FIGO classification grade with MSI phenotype and obesity with MSS phenotype. Given these statistical results, we propose a function for predicting the probability of being MSI phenotype taking into account the histological subtype (endometrioid/non-endometrioid carcinoma) and FIGO grade as well as obesity. This prediction may be useful prior to hysterectomy, for genetic study of the MLH1 promoter and subsequent genetic counseling.

RNA sequencing uncovers clinically actionable germline intronic MSH2 variants in previously unresolved Lynch syndrome families

Despite advances in genetic testing for Lynch syndrome, nearly one quarter of mismatch repair-deficient (MMRd) colorectal and endometrial cancers remain unexplained. When added to germline DNA testing, RNA sequencing can increase diagnostic yield, improve variant classification and reduce variants of uncertain significance. Here, we describe two cases where RNA sequencing uncovered likely pathogenic MSH2 variants in families with MMRd tumours that were initially unexplained following comprehensive genetic testing for Lynch syndrome.

Histological and Somatic Mutational Profiles of Mismatch Repair Deficient Endometrial Tumours of Different Aetiologies

BACKGROUND

Mismatch repair deficient (MMRd) tumours may arise from somatic events acquired during carcinogenesis or in the context of Lynch syndrome (LS), an inherited cancer predisposition condition caused by germline MMR pathogenic variants. Our aim was to explore whether sporadic and hereditary MMRd endometrial cancers (EC) display distinctive tumour biology.

METHODS

Clinically annotated LS-EC were collected. Histological slide review was performed centrally by two specialist gynaecological pathologists. Mutational analysis was by a bespoke 75- gene next-generation sequencing panel. Comparisons were made with sporadic MMRd EC. Multiple correspondence analysis was used to explore similarities and differences between the cohorts.

RESULTS

After exclusions, 135 LS-EC underwent independent histological review, and 64 underwent mutational analysis. Comparisons were made with 59 sporadic MMRd EC. Most tumours were of endometrioid histological subtype (92% LS-EC and 100% sporadic MMRd EC, respectively, p = NS). Sporadic MMRd tumours had significantly fewer tumour infiltrating lymphocytes (p ≤ 0.0001) and showed more squamous/mucinous differentiation than LS-EC (p = 0.04/p = 0.05). PTEN mutations were found in 88% sporadic MMRd and 61% LS-EC, respectively (p < 0.001). Sporadic MMRd tumours had significantly more mutations in PDGFRA, ALK, IDH1, CARD11, CIC, MED12, CCND1, PTPN11, RB1 and KRAS, while LS-EC showed more mutations affecting SMAD4 and ARAF. LS-EC showed a propensity for TGF-β signalling disruption. Cluster analysis found that wild type PTEN associates predominantly with LS-EC, whilst co-occurring mutations in PTEN, PIK3CA and KRAS predict sporadic MMRd EC.

CONCLUSIONS

Whilst MMRd EC of hereditary and sporadic aetiology may be difficult to distinguish by histology alone, differences in infiltrating immune cell counts and mutational profile may predict heterogenous responses to novel targeted therapies and warrant further study.

BRAF V600E and Mismatch Repair Proteins Expression in Sporadic Young-onset Colorectal Cancer in Kelantan, Malaysia

Objectives

We sought to determine the immunohistochemistry expression of mismatch repair (MMR) and BRAF V600E proteins in sporadic young-onset colorectal cancer (CRC) and their association with clinicopathological features in the Kelantan population.

Methods

This was a cross-sectional study of sporadic young-onset CRC over 11 years from 1 January 2006 to 31 December 2017 in Kelantan. Formalin-fixed paraffin-embedded tissue blocks were immunohistochemically stained with antibodies for MMR (MLH1, MSH2, MSH6, and PMS2) and BRAF V600E. These expressions were correlated with clinicopathological parameters.

Results

Our patient sample included 31 patients with a mean age of 31.5 years. More than half (61.3%) of the patients were women. The majority presented with abdominal pain (41.9%), and 71.0% had a tumor located on the right side of the colon, with 83.9% being moderately differentiated adenocarcinoma. The majority of patients presented at stage IV (54.8%). The most frequent pattern was all MMR protein expressions, which constituted patients in the microsatellite stable group (64.5%). Nine (29.0%) were microsatellite instability (MSI-high), and two (6.5%) were MSI-low. Positive BRAF V600E expression was observed in 83.9% of patients. Only histopathological subtypes revealed a significant association with BRAF V600E positive expression (p = 0.015).

Conclusions

The majority of sporadic young-onset CRC presented with abdominal pain and advanced cancer stage. Most were microsatellite stable, and most cases showed positive expressions in all MMR markers and BRAF V600E by immunohistochemistry method. This finding will pave the way for further research on this disease.

Mismatch repair status between primary colorectal tumor and metastatic tumor, a retrospective consistent study

Objectives Mismatch repair (MMR) and Microsatellite instability (MSI) are critical when considering immunotherapy and chemotherapeutic drugs an option for patients with colorectal cancer (CRC). We investigated the consistence of MMR status as well as MSI between primary CRC and metastatic tumor to see if the expression of four MMR proteins and the status of MSI are congruent in primary tumor and metastatic tumor. With the results of the study and future more relevant studies, the sites of MMR testing may be more precise for individualized treatment.

Study design Patients with clear diagnosis of sporadic CRC and distal organ metastasis were identified from a prospectively established database. The status of MMR and MSI was evaluated by immunohistochemistry (IHC) and Polymerase Chain Reaction (PCR) respectively of synchronously obtained tissue samples.

Results Forty patients with complete clinical date were enrolled. For primary tumor, 36/40 samples were tested as MMR-proficient (pMMR) and 4 were MMR-deficient (dMMR). For metastatic samples, 30 samples were tested as pMMR while 10 samples were dMMR. Six out of forty patients were tested as inconsistent status of MMR and MSI. After statistical analysis, the expression status of MMR was not statistically significant between primary and metastatic tumors (P=0.1405, larger than 0.05).

Conclusion Based on our samples, the status of MMR between primary CRC and metastatic tumor was consistent, thus test of MMR status can be performed at both sites. However, due to the limited samples enrolled in our study, the results should be interpreted carefully.

Shrestha T, Zilfalil BA. MLH1 and MSH2 mismatch repair protein profile using immunohistochemistry in Nepalese colorectal cancer patients

BACKGROUND Hereditary nonpolyposis colorectal cancer, or Lynch syndrome, caused by germline mutations or genetic defects in mismatch repair (MMR) genes (MLH1, MSH2, PMS2, MSH6, and epithelial cellular adhesion molecule), is an autosomal dominant condition accounting for 2–5% of all colorectal carcinomas (CRCs). Reports on MMR loss in many populations are available; however, there are no reports on the frequency of MMR protein expression in Nepalese cohorts. Therefore, this study was aimed to assess the expression profiles of MLH1 and MSH2 protein by immunohistochemistry (IHC) in Nepalese CRC patients. METHODS This retrospective study used archived formalin-fixed paraffin-embedded tissue blocks from 43 Nepalese CRC patients. IHC staining was performed using MLH1 and MSH2 antibodies. IHC scoring analysis was assessed using semiquantitative scoring. RESULTS Of the 43 CRC patients, 8 (18.6%) showed loss of staining for MLH1 antibody, 5 (11.6%) showed loss of staining for MSH2 antibody, and 4 (9.3%) showed loss of staining for both MLH1 and MSH2 antibodies. CONCLUSIONS IHC is a potential screening method of determining the MMR expression profile of Nepalese CRC patients. IHC can be performed in local clinical laboratories to find MMR protein defects in selected cases prior to expensive molecular tests.

Distinct Immunological Landscapes Characterize Inherited and Sporadic Mismatch Repair Deficient Endometrial Cancer

Around 30% of endometrial cancers (EC) are mismatch repair (MMR) deficient, mostly as a consequence of mutations acquired during tumorigenesis, but a significant minority is caused by Lynch syndrome (LS). This inherited cancer predisposition syndrome primes an anti-cancer immune response, even in healthy carriers. We sought to explore the intra-tumoral immunological differences between genetically confirmed LS-associated MMR-deficient (MMRd), sporadic MMR-deficient, and MMR-proficient (MMRp) EC. Endometrial tumors from women with known LS were identified (n = 25). Comparator tumors were recruited prospectively and underwent microsatellite instability (MSI) testing, immunohistochemistry (IHC) for MMR expression and MLH1 methylation testing. Those found to have MLH1 hypermethylation formed the sporadic MMR-deficient group (n = 33). Those found to be mismatch repair proficient and microsatellite stable formed the MMR-proficient group (n = 35). A fully automated monoplex IHC panel was performed on sequential formalin-fixed paraffin-embedded tumor sections to identify CD3+, CD8+, CD45RO+, FoxP3+, and PD-1+ immune cells, and PD-L1 expression by tumor/immune cells. Two independent observers quantified immune marker expression at the tumor center and invasive margin. Mean and overall compartmental T-cell counts generated standard (binary: Low/High) and higher resolution (quaternary: 0-25, 25-50, 50-75, 75-100%) immune scores, which were used as explanatory features in neural network, support vector machine, and discriminant predictive modeling. Overall T-cell counts were significantly different between the three cohorts: CD3+ (p = <0.0001), CD8+ (p = <0.0001), CD45RO+ (<0.0001), FoxP3+ (p = <0.0001), and PD1+ (p = <0.0001), with LS-associated MMR-deficient tumors having highest infiltrations. There were significant differences in CD8+ (p = 0.02), CD45RO+ (p = 0.007), and PD-1+ (p = 0.005) T-cell counts at the invasive margin between LS-associated and sporadic MMR-deficient tumors, but not between sporadic MMR-deficient and MMR-proficient tumors. Predictive modeling could accurately determine MMR status based on CD8+ T-cell counts within the tumor center alone. This study shows that LS-associated and sporadic MMR-deficient EC are distinct immunological entities, which has important implications for treatment and prognosis.

Screening for Lynch Syndrome by Immunohistochemistry of Mismatch Repair Proteins: Significance of Indeterminate Result and Correlation With Mutational Studies

CONTEXT.—

Immunohistochemical expression of mismatch repair (MMR) protein is a well-accepted method for routine screening for Lynch syndrome with relatively high sensitivity and specificity. Occasionally, however, immunohistochemistry (IHC) can yield an equivocal result with poor reproducibility and the potential for misdiagnosis.

OBJECTIVE.—

To determine the frequency and significance of indeterminate MMR IHC expression in patients routinely screened for Lynch syndrome and correlation with germline mutation studies.

DESIGN.—

Semiquantitative scoring of MMR IHC was performed by image analysis in 479 cases, of which 380 were colorectal and 99 endometrial cancer. Scores of 10% or more, less than 10%, and 0% were used as cutoffs for retained, indeterminate, and loss of expression, respectively. Negative and indeterminate IHC results were confirmed by mutational studies.

RESULTS.—

Four hundred eighteen of 479 cases (87.2%) were reported as retained expression, 45 (9.3%) as loss of expression, and 16 (3.3%) as indeterminate expression. Fifteen of 45 (33.3%) and 8 of 16 (50%) with loss and indeterminate expression, respectively, were found to have Lynch syndrome by germline studies. The overall frequency of Lynch syndrome in our patient population was 4.8% (23 of 479), and 34.7% of these (8 of 23) were associated with indeterminate IHC expression. In the indeterminate group, MLH1 germline mutation was the most frequent (6 of 13; 46.2%), followed by MSH6 (4 of 13; 30.7%).

CONCLUSIONS.—

Our findings provide further evidence that indeterminate IHC should be further investigated for possible MMR germline mutation. Guidelines for interpretation of MMR IHC and the establishment of more objective criteria for defining indeterminate results are important to improve the sensitivity and specificity of the IHC assay.

A systematic review and economic evaluation of diagnostic strategies for Lynch syndrome

BACKGROUND

Lynch syndrome (LS) is an inherited autosomal dominant disorder characterised by an increased risk of colorectal cancer (CRC) and other cancers, and caused by mutations in the deoxyribonucleic acid (DNA) mismatch repair genes.

OBJECTIVE

To evaluate the accuracy and cost-effectiveness of strategies to identify LS in newly diagnosed early-onset CRC patients (aged < 50 years). Cascade testing of relatives is employed in all strategies for individuals in whom LS is identified.

DATA SOURCES AND METHODS

Systematic reviews were conducted of the test accuracy of microsatellite instability (MSI) testing or immunohistochemistry (IHC) in individuals with CRC at risk of LS, and of economic evidence relating to diagnostic strategies for LS. Reviews were carried out in April 2012 (test accuracy); and in February 2012, repeated in February 2013 (economic evaluations). Databases searched included MEDLINE (1946 to April week 3, 2012), EMBASE (1980 to week 17, 2012) and Web of Science (inception to 30 April 2012), and risk of bias for test accuracy was assessed using the Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2) quality appraisal tool. A de novo economic model of diagnostic strategies for LS was developed.

RESULTS

Inconsistencies in study designs precluded pooling of diagnostic test accuracy results from a previous systematic review and nine subsequent primary studies. These were of mixed quality, with significant methodological concerns identified for most. IHC and MSI can both play a part in diagnosing LS but neither is gold standard. No UK studies evaluated the cost-effectiveness of diagnosing and managing LS, although studies from other countries generally found some strategies to be cost-effective compared with no testing. The de novo model demonstrated that all strategies were cost-effective compared with no testing at a threshold of £20,000 per quality-adjusted life-year (QALY), with the most cost-effective strategy utilising MSI and BRAF testing [incremental cost-effectiveness ratio (ICER) = £5491 per QALY]. The maximum health benefit to the population of interest would be obtained using universal germline testing, but this would not be a cost-effective use of NHS resources compared with the next best strategy. When the age limit was raised from 50 to 60 and 70 years, the ICERs compared with no testing increased but remained below £20,000 per QALY (except for universal germline testing with an age limit of 70 years). The total net health benefit increased with the age limit as more individuals with LS were identified. Uncertainty was evaluated through univariate sensitivity analyses, which suggested that the parameters substantially affecting cost-effectiveness: were the risk of CRC for individuals with LS; the average number of relatives identified per index patient; the effectiveness of colonoscopy in preventing metachronous CRC; the cost of colonoscopy; the duration of the psychological impact of genetic testing on health-related quality of life (HRQoL); and the impact of prophylactic hysterectomy and bilateral salpingo-oophorectomy on HRQoL (this had the potential to make all testing strategies more expensive and less effective than no testing).

LIMITATIONS

The absence of high-quality data for the impact of prophylactic gynaecological surgery and the psychological impact of genetic testing on HRQoL is an acknowledged limitation.

CONCLUSIONS

Results suggest that reflex testing for LS in newly diagnosed CRC patients aged < 50 years is cost-effective. Such testing may also be cost-effective in newly diagnosed CRC patients aged < 60 or < 70 years. Results are subject to uncertainty due to a number of parameters, for some of which good estimates were not identified. We recommend future research to estimate the cost-effectiveness of testing for LS in individuals with newly diagnosed endometrial or ovarian cancer, and the inclusion of aspirin chemoprevention. Further research is required to accurately estimate the impact of interventions on HRQoL.

STUDY REGISTRATION

This study is registered as PROSPERO CRD42012002436.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

Analysis of Hereditary Nonpolyposis Colorectal Cancer in Malay Cohorts using Immunohistochemical Screening

BACKGROUND

Lynch syndrome (LS) is an inherited predisposition to colorectal, endometrial (uterine) and other cancers. Although most cancers are not inherited, about 5 percent (%) of people who have colorectal or endometrial cancer have the Lynch syndrome. It involves the alteration of mismatch repair (MMR) genes; MLH1, MSH2, MSH6 or PMS2. In this study, we analyzed the expression of MMR proteins in colorectal cancer in a Malay cohort by immunohistochemistry.

MATERIALS AND METHODS

A total of 17 patients were selected fulfilling one of the Bethesda criteria: colorectal cancer diagnosed in a patient aged less than 50 years old, having synchronous and metachronous colorectal cancer or with a strong family history. Immunohistochemical staining was performed on paraffin embedded tumour tissue samples using four antibodies: MLH1, MSH2, MSH6 and PMS2.

RESULTS

Twelve out of 17 patients (70.6%) were noted to have a family history. A total of 41% (n=7) of the patients had abnormal immunohistochemical staining with one or more of the four antibodies. Loss of expression were noted in 13 tumour tissues with a negative staining score <4. Of 13 tumour tissues, four showed loss expression of MLH1. For PMS2, loss of expression were noted in five cases. Both MSH2 and MSH6 showed loss of expression in two tumour tissues respectively.

CONCLUSIONS

Revised Bethesda criteria and immunohistochemical analysis constituted a convenient approach and is recommended to be a first-line screening for Lynch syndrome in Malay cohorts.

Tumour MLH1 promoter region methylation testing is an effective prescreen for Lynch Syndrome (HNPCC)

BACKGROUND AND AIMS

Lynch syndrome (LS) patients have DNA mismatch repair deficiency and up to 80% lifetime risk of colorectal cancer (CRC). Screening of mutation carriers reduces CRC incidence and mortality. Selection for constitutional mutation testing relies on family history (Amsterdam and Bethesda Guidelines) and tumour-derived biomarkers. Initial biomarker analysis uses mismatch repair protein immunohistochemistry and microsatellite instability. Abnormalities in either identify mismatch repair deficiency but do not differentiate sporadic epigenetic defects, due to MLH1 promoter region methylation (13% of CRCs) from LS (4% of CRCs). A diagnostic biomarker capable of making this distinction would be valuable. This study compared two biomarkers in tumours with mismatch repair deficiency; quantification of methylation of the MLH1 promoter region using a novel assay and BRAF c.1799T>A, p.(Val600Glu) mutation status in the identification of constitutional mutations.

METHODS

Tumour DNA was extracted (formalin fixed, paraffin embedded, FFPE tissue) and pyrosequencing used to test for MLH1 promoter methylation and presence of the BRAF c.1799T>A, p.(Val600Glu) mutation 71 CRCs from individuals with pathogenic MLH1 mutations and 73 CRCs with sporadic MLH1 loss. Specificity and sensitivity was compared.

FINDINGSS

Unmethylated MLH1 promoter: sensitivity 94.4% (95% CI 86.2% to 98.4%), specificity 87.7% (95% CI 77.9% to 94.2%), Wild-type BRAF (codon 600): sensitivity 65.8% (95% CI 53.7% to 76.5%), specificity 98.6% (95% CI 92.4% to 100.0%) for the identification of those with pathogenic MLH1 mutations.

CONCLUSIONS

Quantitative MLH1 promoter region methylation using pyrosequencing is superior to BRAF codon 600 mutation status in identifying constitutional mutations in mismatch repair deficient tumours.

MutSα and MutLα immunoexpression analysis in diagnostic grading of oral epithelial dysplasia and squamous cell carcinoma

OBJECTIVES

This study explored the expression of DNA mismatch repair (MMR) proteins in a range of oral biopsies. We further evaluated the significance of MMR protein expression combined with basic demographic data in differentiating grades of oral epithelial dysplasia (OED) and oral squamous cell carcinoma (OSCC).

STUDY DESIGN

Immunohistochemical expression of MutSα (hMLH1 and hPMS2) and MutLα (hMSH2 and hMSH6) were compared in 98 formalin-fixed paraffin embedded oral biopsies: 21 normal, 24 mild-dysplasia (MD), 8 moderate-to-severe-dysplasia (SD), and 45 OSCC.

RESULTS

Expression of hMLH1, hPMS2, and hMSH2 was reduced in MD, SD, and OSCC compared with the normal. Reduced hMSH2 immunoreactivity discriminated poorly differentiated OSCC from well-differentiated OSCC. The diagnostic model correctly classified 71.4% of cases and revealed that hPMS2-negative biopsies were more likely to be cancerous (odds ratio [OR], 0.11; 95% confidence interval [CI], 0.000-0.813; P = .040).

CONCLUSION

The results suggested a diagnostic role for MMR proteins in OED and OSCC.

Metachronous colorectal cancer risk in patients with a moderate family history

AIM

Lifetime risk of a metachronous colorectal cancer (mCRC) is 0.6-3% following sporadic colorectal cancer (CRC) and 15-26% in Lynch syndrome. The lifetime incidence of CRC in individuals with moderate familial risk is 8-17%. Risk of mCRC is unknown.

METHOD

A retrospective longitudinal study of the Regional Familial CRC Registry was performed. Patients who had at least one CRC were categorized as follows: moderate risk (n = 383), Lynch syndrome (n = 528) and average (population) risk (n = 409). The Kaplan-Meier estimate (1-KM) and the cumulative incidence function were used to calculate the risk of mCRC. The 1-KM gives the risk for individuals remaining at risk (alive) at a given time point and thus is useful for counselling. The cumulative incidence function gives the risk for the whole population.

RESULTS

The 1-KM and the cumulative incidence function demonstrated that the risk of mCRC was significantly higher in moderate-risk patients compared with average (population)-risk patients (1-KM, P = 0.008; cumulative incidence function, P = 0.00097). However, the risk of mCRC was higher in patients with Lynch syndrome than in moderate-risk or average (population)-risk patients. The 1-KM in moderate-risk patients was 2.7%, 6.3% and 23.5% at 5, 10 and 20 years, respectively. In average (population)-risk patients, the 1-KM was 1.3%, 3.1% and 7.0% at 5, 10 and 20 years, and the cumulative incidence function was 0.3%, 0.6% and 2.4% at the same time points, respectively.

CONCLUSION

These data indicate that the risk of mCRC is significantly higher in patients with a moderate family history of CRC than in those with an average (population) risk. This justifies proactive lifelong surveillance.

Lynch or not Lynch? Is that always a question?

The familial cancer syndrome referred to as Lynch I and II was renamed hereditary nonpolyposis colorectal cancer (HNPCC) only to revert later to Lynch syndrome (LS). LS is the most frequent human predisposition for the development of colorectal cancer (CRC), and probably also for endometrial and gastric cancers, although it has yet to acquire a consensus name. Its estimated prevalence ranges widely from 2% to 7% of all CRCs due to the fact that tumors from patients with LS are difficult to recognize at both the clinical and molecular level. This review is based on two assumptions. First, all LS patients inherit a predisposition to develop CRC (without polyposis) and/or other tumors from the Lynch spectrum. Second, all LS patients have a germline defect in one of the DNA mismatch repair (MMR) genes. When a somatic second hit inactivates the relevant MMR gene, the consequence is instability of DNA repeat sequences such as microsatellites and the tumors are referred to as having the microsatellite instability (MSI) phenotype. However, some of the inherited predisposition to develop CRC without concurrent polyposis, termed HNPCC, is found in non-LS patients, while not all MSI tumors are from LS cases. LS tumors are therefore at the junction of inherited and MSI cases. We describe here the defining characteristics of LS tumors that differentiate them from inherited non-MSI tumors and from non-inherited MSI tumors.

FANCJ expression predicts the response to 5-fluorouracil-based chemotherapy in MLH1-proficient colorectal cancer

PURPOSE

Fanconi anemia protein, FANCJ, directly interacts with MLH1, a key protein involved in DNA mismatch repair. Deficient mismatch repair, or microsatellite instability, is a potent marker for the ineffectiveness of 5-fluorouracil (5-FU) in colorectal cancer (CRC). We investigated the significance of FANCJ expression in CRC, focusing on the effects of 5-FU-based adjuvant chemotherapy.

METHODS

Clinicopathologic features and immunohistochemical expression of FANCJ and MLH1 were studied in 219 patients with CRC. We also analyzed 5-FU sensitivity in CRC cell lines with varying levels of FANCJ expression.

RESULTS

FANCJ expression was elevated in tumor tissues compared with normal epithelial tissue. High expression of FANCJ was significantly associated with 5-FU resistance measured by the SDI test (P < 0.05) and poor recurrence-free survival (RFS) (P < 0.05). Among patients with stage II/III tumors who received 5-FU, patients with tumors exhibiting high FANCJ expression had significantly worse RFS than did patients with tumors exhibiting low FANCJ expression (P < 0.01). Among patients who did not receive adjuvant chemotherapy, FANCJ expression was not correlated with RFS (P = 0.76). High FANCJ expression was correlated with 5-FU resistance in tumors with normal MLH1 expression (P < 0.05) but not in tumors not expressing MLH1 (P = 0.9). In vitro, FANCJ overexpression was correlated with 5-FU resistance in MLH1-proficient HCT116 3-6 cells but not in MLH1-deficient HCT116 cells.

CONCLUSIONS

FANCJ could be a useful biomarker to predict the response to 5-FU and prognosis of CRC, particularly in tumors with normal MLH1 expression.

Analysis of DNA mismatch repair proteins expression and BRAF V600E mutation in a subset of early- and late-onset colorectal carcinoma patients in Mexico

BACKGROUND AND AIMS

A third of colorectal carcinomas (CRC) affect patients <50 years of age. Fifteen percent of CRC cases with microsatellite instability are due to inherited germ-line mutations in DNA mismatch repair genes. The rest have an epigenetic hypermethylation of the MLH1 promoter in whom the BRAF V600E mutation is a common hallmark. Immunohistochemistry helps to classify colorectal cancers with 100% specificity and 92% sensitivity. We undertook this study to determine if age is a risk factor for defective MMR protein expression and BRAF mutations in our population and to compare these results with the histopathological tumor features.

METHODS

Immunohistochemistry for MLH1 and MSH2 and RT-PCR BRAF V600E mutation was performed on tissue specimens from 57 patients <50 years of age. Data on age, gender, tumor location, histology, depth of infiltration, and the presence of metastatic lymph nodes were collected. Forty eight patients >50 years of age were used as a control group. A statistical analysis using ANOVA, χ(2), and Spearman's rho test were performed.

RESULTS

Absent MMR protein expression was more prevalent in patients <50 years of age. No BRAF V600E mutations were detected in either group. Medullary and mucinous types were more prevalent among young patients, whereas intestinal type was more frequent in older patients (p = 0.0008). No differences were found regarding clinicopathological stages between groups.

CONCLUSIONS

We found an association between young age and defective MMR expression. No V600E BRAF mutations were detected in either group.

Challenging cases encountered in colorectal cancer screening for Lynch syndrome reveal novel findings: nucleolar MSH6 staining and impact of prior chemoradiation therapy

Many pathology laboratories have developed specific screening protocols to detect patients with Lynch syndrome. With recent recommendations to test all patients with newly diagnosed colorectal cancer for Lynch syndrome, the volume of testing will increase, and the most economic and reliable screening test will prevail. Although the detection of microsatellite instability by polymerase chain reaction and the detection of loss of the mismatch repair proteins by immunohistochemistry can each be used as a screening tool, each methodology has its strengths and weaknesses. During the time of our study, we used both polymerase chain reaction and immunohistochemistry to screen for Lynch syndrome in colorectal cancer specimens. We encountered 21 cases that posed significant interpretive challenges. A previously unpublished pattern of nucleolar MSH6 staining and potential spurious results induced by chemoradiation therapy are described. We feel that it is important to report these cases so that potential pitfalls in screening for Lynch syndrome can be avoided.

A comparative study of quantitative immunohistochemistry and quantum dot immunohistochemistry for mutation carrier identification in Lynch syndrome

Aims

Lynch Syndrome is caused by mutations in DNA mismatch repair (MMR) genes. Mutation carrier identification is facilitated by immunohistochemical detection of the MMR proteins MHL1 and MSH2 in tumour tissue and is desirable as colonoscopic screening reduces mortality. However, protein detection by conventional immunohistochemistry (IHC) is subjective, and quantitative techniques are required. Quantum dots (QDs) are novel fluorescent labels that enable quantitative multiplex staining. This study compared their use with quantitative 3,3′-diaminobenzidine (DAB) IHC for the diagnosis of Lynch Syndrome.

Methods

Tumour sections from 36 mutation carriers and six controls were obtained. These were stained with DAB on an automated platform using antibodies against MLH1 and MSH2. Multiplex QD immunofluorescent staining of the sections was performed using antibodies against MLH1, MSH2 and smooth muscle actin (SMA). Multispectral analysis of the slides was performed. The staining intensity of DAB and QDs was measured in multiple colonic crypts, and the mean intensity scores calculated. Receiver operating characteristic (ROC) curves of staining performance for the identification of mutation carriers were evaluated.

Results

For quantitative DAB IHC, the area under the MLH1 ROC curve was 0.872 (95% CI 0.763 to 0.981), and the area under the MSH2 ROC curve was 0.832 (95% CI 0.704 to 0.960). For quantitative QD IHC, the area under the MLH1 ROC curve was 0.812 (95% CI 0.681 to 0.943), and the area under the MSH2 ROC curve was 0.598 (95% CI 0.418 to 0.777).

Conclusions

Despite the advantage of QD staining to enable several markers to be measured simultaneously, it is of lower utility than DAB IHC for the identification of MMR mutation carriers. Automated DAB IHC staining and quantitative slide analysis may enable high-throughput IHC.