Revised Bethesda Guidelines Research Articles

Rectal Cancer Diagnosed after Cesarean Section in Which High Microsatellite Instability Indicated the Presence of Lynch Syndrome.

We report a case of rectal cancer with microsatellite instability (MSI) that probably resulted from Lynch syndrome and that was diagnosed after Cesarean section. The patient was a 28-year-old woman (gravid 1, para 1) without a significant medical history. At 35 gestational weeks, vaginal ultrasonography revealed a 5 cm tumor behind the uterine cervix, which was diagnosed as a uterine myoma. The tumor gradually increased in size and blocked the birth canal, resulting in the patient undergoing an emergency Cesarean section. Postoperatively, the tumor was diagnosed as rectal cancer with MSI. After concurrent chemoradiation therapy, a lower anterior resection was performed. The patient's family history revealed she met the criteria of the revised Bethesda guidelines for testing the colorectal tumor for MSI. Testing revealed that the tumor did indeed show high MSI and, combined with the family history, suggested this could be a case of Lynch syndrome. Our findings emphasize the importance of considering the possibility of Lynch syndrome in pregnant women with colorectal cancer, particularly those with a family history of this condition. We suggest that the presence of Lynch syndrome should also be considered for any young woman with endometrial, ovarian, or colorectal cancer.

Clinicopathological and genetic features of Chinese hereditary nonpolyposis colorectal cancer (HNPCC)

The aim of this study was to investigate the clinical value of different criteria and to understand the relationship between genotype and phenotype in Chinese hereditary nonpolyposis colorectal cancer (HNPCC). A total of 116 unrelated probands of suspected HNPCC families from the Fudan Colorectal Registry were studied. A total of 32, 28, and 56 families fulfilled the Amsterdam criteria, the Fudan criteria and the revised Bethesda guideline, respectively. Direct DNA sequencing of all exons of hMSH2 and hMLH1 genes were performed on all 116 samples. Mutations and clinicopathological features were compared between the groups. Thirty-two pathological germline mutations were identified. Out of 32 mutations, 16 were located at hMLH1 and 16 at hMSH2. The sensitivity of Amsterdam criteria was 50 %, specificity was 81 %, and Youden’s index was 31 %. The sensitivity of Fudan criteria was 75 %, specificity was 58 %, and Youden’s index was 33 %. Among all the 32 families with mutations, families with hMSH2 mutation had a higher ratio of synchronous and metachronous colon cancers than families with hMLH1 mutation (33 vs. 6 %, P = 0.04). Patients with hMSH2 mutation more frequently harbour synchronous and metachronous colon cancers. Fudan criteria had a little higher sensitivity and accuracy than Amsterdam criteria for identification of Chinese HNPCC.

The histomorphology of Lynch syndrome-associated ovarian carcinomas: toward a subtype-specific screening strategy.

Women with Lynch syndrome (LS) are at increased risk for the development of epithelial ovarian cancer (OC). Analogous to previous studies on BRCA1/2 mutation carriers, there is evidence to suggest a histotype-specific association in LS-associated OCs (LS-OC). Whereas the diagnosis of high-grade serous carcinoma is an indication for BRCA1/2 germline testing, in contrast, there are no screening guidelines in place for triaging OC patients for LS testing based on histotype. We performed a centralized pathology review of tumor subtype on 20 germline mutation-confirmed LS-OCs, on the basis of morphologic assessment of hematoxylin and eosin-stained slides, with confirmation by immunohistochemistry when necessary. Results from mismatch-repair immunohistochemistry (MMR-IHC) and microsatellite instability (MSI) phenotype status were documented, and detailed pedigrees were analyzed to determine whether previously proposed clinical criteria would have selected these patients for genetic testing. Review of pathology revealed all LS-OCs to be either pure endometrioid carcinoma (14 cases), mixed carcinoma with an endometrioid component (4 cases), or clear cell carcinoma (2 cases). No high-grade or low-grade serous carcinomas or mucinous carcinomas of intestinal type were identified. Tumor-infiltrating lymphocytes were prominent (≥40 per 10 high-powered fields) in 2 cases only. With the exception of 1 case, all tumors tested for MMR-IHC or MSI had an MMR-deficient phenotype. Within this cohort, 50%, 55%, 65%, and 85% of patients would have been selected for genetic workup by Amsterdam II, revised Bethesda Guidelines, SGO 10% to 25%, and SGO 5% to 10% criteria, respectively, with <60% of index or sentinel cases detected by any of these schemas. To further support a subtype-driven screening strategy, MMR-IHC reflex testing was performed on all consecutive non-serous OCs diagnosed at 1 academic hospital over a 2-year period; MMR deficiency was identified in 10/48 (21%) cases, all with endometrioid or clear cell histology. We conclude that there is a strong association between endometrioid and clear cell ovarian carcinomas and hereditary predisposition due to MMR gene mutation. These findings have implications for the role of tumor subtype in screening patients with OC for further genetic testing and support reflex MMR-IHC and/or MSI testing for newly diagnosed cases of endometrioid or clear cell ovarian carcinoma.

491PD - Lynch-Like Syndrome: Characterization and Comparison with Epcam Deletion Carriers

ABSTRACT Introduction: Colorectal cancers (CRCs) with MSI+ but without detectable germline mutation or hypermethylation in DNA mismatch repair (MMR) genes can be classified as Lynch-like Syndrome (LLS). The underlying mechanism and clinical significances of LLS are largely unknown. Methods: We measured MSI and MMR protein expression in 4,765 consecutive CRC cases. Among these, MSI+ cases were further classified based on clinical parameters, sequencing of MMR genes or polymerase e (POLE) and d (POLD1) and promoter methylation analysis of MLH1 and MSH2. Results: We found that MSI+ and MMR protein deficient CRCs comprised 6.3% (N = 302) of this cohort. Based on germline sequencing of 124 cases, we identified 54 LS with MMR germline mutation (LS-MMR), 15 LS with EPCAM deletions (LS-EPCAM) and 55 LLS patients. Of the 55 LLS patients, six (10.9%) had variants of unknown significance in the genes tested, and one patient had a novel somatic mutation (p.S459P) in POLE. In patients with biallelic deletions of EPCAM, all tumors and their matched normal mucosa showed promoter hypermethylation of MSH2. Conclusion: We found that patients with LLS and LS-EPCAM shared clinical features that differed from LS-MMR patients, including lower frequency of fulfillment of the revised Bethesda guidelines (83.6% and 86.7% vs. 98.1% for LS-MMR) and older mean age at CRC diagnosis (52.6 and 52.7 years vs. 43.9 years for LS-MMR). The similarity between LLS and LS-EPCAM suggests LLS as a subset of familial MSI+ CRC. Disclosure: All authors have declared no conflicts of interest.

Lynch-like syndrome: characterization and comparison with EPCAM deletion carriers.

Colorectal cancers (CRCs) with microsatellite instability-high (MSI+) but without detectable germline mutation or hypermethylation in DNA mismatch repair (MMR) genes can be classified as Lynch-like syndrome (LLS). The underlying mechanism and clinical significances of LLS are largely unknown. We measured MSI and MMR protein expression in 4,765 consecutive CRC cases. Among these, MSI+ cases were further classified based on clinical parameters, germline sequencing of MMR genes or polymerase ε (POLE) and δ (POLD1) and promoter methylation analysis of MLH1 and MSH2. We found that MSI+ and MMR protein-deficient CRCs comprised 6.3% (N = 302) of this cohort. On the basis of germline sequencing of 124 cases, we identified 54 LS with MMR germline mutation (LS-MMR), 15 LS with EPCAM deletions (LS-EPCAM) and 55 LLS patients. Of the 55 LLS patients, six (10.9%) had variants of unknown significance in the genes tested, and one patient had a novel somatic mutation (p.S459P) in POLE. In patients with biallelic deletions of EPCAM, all tumors and their matched normal mucosa showed promoter hypermethylation of MSH2. Finally, we found that patients with LLS and LS-EPCAM shared clinical features that differed from LS-MMR patients, including lower frequency of fulfillment of the revised Bethesda guidelines (83.6 and 86.7% vs. 98.1% for LS-MMR) and older mean age at CRC diagnosis (52.6 and 52.7 years vs. 43.9 years for LS-MMR). We identified somatic mutation in POLE as a rare underlying cause for MMR deficiency in LLS. The similarity between LLS and LS-EPCAM suggests LLS as a subset of familial MSI+ CRC.

The mutational spectrum of Lynch syndrome in cyprus.

Lynch syndrome is the most common form of hereditary colorectal cancer and is caused by germline mutations in the mismatch repair (MMR) genes MLH1, MSH2, MSH6 and PMS2. Mutation carriers have an increased lifetime risk of developing colorectal cancer as well as other extracolonic tumours. The aim of the current study was to evaluate the frequency and distribution of mutations in the MLH1, MSH2 and MSH6 genes within a cohort of Cypriot families that fulfilled the revised Bethesda guidelines. The study cohort included 77 patients who fulfilled at least one of the revised Bethesda guidelines. Mutational analysis revealed the presence of 4 pathogenic mutations, 3 in the MLH1 gene and 1 in the MSH2 gene, in 5 unrelated individuals. It is noted that out of the 4 pathogenic mutations detected, one is novel (c.1610delG in exon 14 of the MLH1) and has been detected for the first time in the Cypriot population. Overall, the pathogenic mutation detection rate in our patient cohort was 7%. This percentage is relatively low but could be explained by the fact that the sole criterion for genetic screening was compliance to the revised Bethesda guidelines. Larger numbers of Lynch syndrome families and screening of the two additional predisposition genes, PMS2 and EPCAM, are needed in order to decipher the full spectrum of mutations associated with Lynch syndrome predisposition in Cyprus.

Pathological stage significantly predicts survival in colorectal cancer patients: a study from two tertiary care centers in India

SUMMARY Aims: An increase in incidence of early-onset colorectal cancer (EOCRC) in developing countries, including India, is reported recently; however, systematic analyses of clinico-pathological features and disease prognosis has seldom been undertaken. Materials &amp; methods: We studied clinical data pertaining to 1259 colorectal adenocarcinoma patients from two tertiary cancer centers in south India. Results: Approximately 45% of patients were aged below 50 years and poor grade and late-stage tumors were significantly associated with early disease onset. Although tumor grade and stage significantly influenced disease-free survival independently, significant association between survival and age of onset or tumor location was not detected unlike previous observations. Conclusion: Given the sizeable proportion of EOCRC, implementation of the revised Bethesda guidelines may not be tenable in India. More importantly, the previous observation of EOCRC being significantly associated with poor survival could, in part, be due to a higher proportion of advanced-stage tumors.

Cost-effectiveness and diagnostic effectiveness analyses of multiple algorithms for the diagnosis of Lynch syndrome.

The optimal algorithm to identify Lynch syndrome (LS) among patients with colorectal cancer (CRC) is unclear. The definitive test for LS, germline testing, is too expensive to be applied in all cases. Initial screening with the revised Bethesda Guidelines (RBG) cannot be applied in a considerable number of cases due to missing information. We developed a model to evaluate the cost-effectiveness of 10 strategies for diagnosing LS. Three main issues are addressed: modeling estimates (20-40%) of RBG applicability; comparing sequential or parallel use of microsatellite instability (MSI) and immunohistochemistry (IHC); and a threshold analysis of the charge value below which universal germline testing becomes the most cost-effective strategy. LS detection rates in RBG-based strategies decreased to 64.1-70.6% with 20% inapplicable RBG. The strategy that uses MSI alone had lower yield, but also lower cost than strategies that use MSI sequentially or in parallel with IHC. The use of MSI and IHC in parallel was less affected by variations in the sensitivity and specificity of these tests. Universal germline testing had the highest yield and the highest cost of all strategies. The model estimated that if charges for germline testing drop to $633-1,518, universal testing of all newly diagnosed CRC cases becomes the most cost-effective strategy. The low applicability of RBG makes strategies employing initial laboratory-based testing more cost-effective. Of these strategies, parallel testing with MSI and IHC offers the most robust yield. With a considerable drop in cost, universal germline testing may become the most cost-effective strategy for the diagnosis of LS.

Systematic Study on Genetic and Epimutational Profile of a Cohort of Amsterdam Criteria-Defined Lynch Syndrome in Singapore

BackgroundGermline defects of mismatch repair (MMR) genes underlie Lynch Syndrome (LS). We aimed to gain comprehensive genetic and epigenetic profiles of LS families in Singapore, which will facilitate efficient molecular diagnosis of LS in Singapore and the region.MethodsFifty nine unrelated families were studied. Mutations in exons, splice-site junctions and promoters of five MMR genes were scanned by high resolution melting assay followed by DNA sequencing, large fragment deletions/duplications and promoter methylation in MLH1, MSH2, MSH6 and PMS2 were evaluated by multiplex ligation-dependent probe amplification. Tumor microsatellite instability (MSI) was assessed with five mononucleotide markers and immunohistochemical staining (IHC) was also performed.ResultsPathogenic defects, all confined to MLH1 and MSH2, were identified in 17 out of 59 (28.8%) families. The mutational spectrum was highly heterogeneous and 28 novel variants were identified. One recurrent mutation in MLH1 (c.793C>T) was also observed. 92.9% sensitivity for indication of germline mutations conferred by IHC surpassed 64.3% sensitivity by MSI. Furthermore, 15.6% patients with MSS tumors harbored pathogenic mutations.ConclusionsAmong major ethnic groups in Singapore, all pathogenic germline defects were confined to MLH1 and MSH2. Caution should be applied when the Amsterdam criteria and consensus microsatellite marker panel recommended in the revised Bethesda guidelines are applied to the local context. We recommend a screening strategy for the local LS by starting with tumor IHC and the hotspot mutation testing at MLH1 c.793C>T followed by comprehensive mutation scanning in MLH1 and MSH2 prior to proceeding to other MMR genes.

Limited diagnostic value of microsatellite instability associated pathology features in colorectal cancer

To determine the diagnostic test characteristics and inter-observer variation of pathology features for identifying high microsatellite instability (MSI-H) colorectal cancer (CRC). Six pathologists blindly evaluated 177 CRC for the presence of MSI-H associated pathology features. Inter-observer agreement was determined by using Kappa-statistics. In the first random 88/177 cases, mucinous carcinoma, tumor-infiltrating lymphocytes (TIL) and Crohns-like infiltrate (CLI) were the best discriminators between MSI-H and microsatellite stable CRC [OR 5.6 (95% CI 1.7-19), 5.4 (1.8-17) and 3.5 (1.1-11), respectively], with high specificity (89-91%). The sensitivities for MSI-H, however, were low (31-41%). In addition, inter-observer agreement was moderate for TIL and CLI (κ 0.38 and 0.48, respectively), but very good for mucinous carcinoma (κ 0.86). Interpretation of overall histopathology as suggestive for MSI-H performed better than any individual feature; OR 15 (5.2-44), and area under the curve 0.79. However, inter-observer agreement was moderate (κ 0.53). In the second set, TIL and CLI were scored according to updated scoring systems. Although both remained the best individual discriminators, test characteristics and inter-observer agreement did not improve. MSI-H pathology features have moderate accuracy for identifying MSI-H CRC, and are identified with moderate inter-observer agreement. These findings highlight the limitations of clinical strategies, such as the revised Bethesda guidelines, which incorporate the MSI-H associated pathology features in their strategy to identify persons with lynch syndrome.

Mismatch repair protein immunohistochemistry: a useful population screening strategy for Lynch syndrome.

Lynch syndrome (LS), the most frequent form of hereditary colorectal cancer, shows a highly penetrant, autosomal dominant pattern of inheritance. Distinction of LS colorectal carcinoma instances from the much more common sporadic colorectal carcinoma cases is of paramount importance. Revised Bethesda Guidelines were developed to diagnose LS by evaluating a combination of clinical and pathologic data. The aim of the present study was to evaluate the usefulness of the pathology items included in the Revised Bethesda Guidelines. We have prospectively studied a series of 1624 consecutive colorectal carcinomas with an algorithm including immunohistochemical analysis of mismatch repair proteins and molecular study of microsatellite instability and BRAF c.1799 T > A (p.V600E) gene mutations. Patients with tumors showing LS features were referred for germline mutation analysis. By applying our algorithmic approach, we were able to identify LS features in 89 colorectal cancer patients, of whom only 27 met Revised Bethesda Guidelines pathology criteria. Of the 89 patients, 47 were then studied at the Genetic Counseling Unit, and LS was confirmed in 18, of whom 7 had not been identified by the Revised Bethesda Guidelines. Our study shows that the Revised Bethesda Guidelines failed to detect 70% of patients at risk of LS. Our algorithmic approach is a realistic and effective tool for LS identification. We strongly recommend the implementation of universal population screening for LS among all patients with newly diagnosed colorectal carcinoma.

Evaluating the performance of clinical criteria for predicting mismatch repair gene mutations in Lynch syndrome: A comprehensive analysis of 3,671 families

Carriers of mismatch repair (MMR) gene mutations have a high lifetime risk for colorectal and endometrial cancers, as well as other malignancies. As mutation analysis to detect these patients is expensive and time-consuming, clinical criteria and tumor-tissue analysis are widely used as pre-screening methods. The aim of our study was to evaluate the performance of commonly applied clinical criteria (the Amsterdam I and II Criteria, and the original and revised Bethesda Guidelines) and the results of tumor-tissue analysis in predicting MMR gene mutations. We analyzed 3,671 families from the German HNPCC Registry and divided them into nine mutually exclusive groups with different clinical criteria. A total of 680 families (18.5%) were found to have a pathogenic MMR gene mutation. Among all 1,284 families with microsatellite instability-high (MSI-H) colorectal cancer, the overall mutation detection rate was 53.0%. Mutation frequencies and their distribution between the four MMR genes differed significantly between clinical groups (p < 0.001). The highest frequencies were found in families fulfilling the Amsterdam Criteria (46.4%). Families with loss of MSH2 expression had higher mutation detection rates (69.5%) than families with loss of MLH1 expression (43.1%). MMR mutations were found significantly more often in families with at least one MSI-H small-bowel cancer (p < 0.001). No MMR mutations were found among patients under 40-years-old with only colorectal adenoma. Familial clustering of Lynch syndrome-related tumors, early age of onset, and familial occurrence of small-bowel cancer were clinically relevant predictors for Lynch syndrome.

Microsatellite Instability Testing in Colorectal Carcinoma: A Practical Guide

In this month’s “Road Ahead” article, we continue last month’s theme that focused on the role of pathology in the care of our GI patients. Many gastroenterologists have successfully incorporated pathology into their core practices either within a business infrastructure or as part of a larger health care system. Dr Gibson and her colleagues at Yale University School of Medicine have helped inform us about a particularly difficult management problem: how to handle the genetically high-risk patients we see frequently in our hospitals and endoscopy units. New comprehensive practice guidelines concerning management of hereditary colon cancer syndromes are in development, but this short article provides a clear and concise guide for the practicing gastroenterologist.

HMLH1 promoter methylation and BRAF mutations in high-frequency microsatellite instability colorectal cancers not fulfilling the revised Bethesda guidelines.

PurposeSporadic colorectal cancers with high-frequency microsatellite instability (MSI-H) are related to hypermethylation of mismatch repair (MMR) genes and a higher frequency of BRAF mutations than Lynch syndrome. We estimated the feasibility of hereditary colorectal cancer based on hMLH1 methylation and BRAF mutations.MethodsBetween May 2005 and June 2011, we enrolled all 33 analyzed patients with MSI-H cancer (male:female, 23:10; mean age, 65.5 ± 9.4 years) from a prospectively maintained database that didn't match Bethesda guidelines and who had results of hMLH1 methylation and BRAF mutations.ResultsAmong the 33 patients, hMLH1 promoter methylation was observed in 36.4% (n = 12), and was not significantly related with clinicopathologic variables, including MLH1 expression. BRAF mutations were observed in 33.3% of the patients (n = 11). Four of 11 and five of 22 patients with MSI-H colon cancers were BRAF mutation (+)/hMLH1 promoter methylation (-) or BRAF mutation (-)/hMLH1 promoter methylation (+). Of the 33 patients, 21.2% were BRAF mutation (+)/hMLH1 promoter methylation (+), indicating sporadic cancers. Seventeen patients (51.5%) were BRAF mutation (-)/hMLH1 promoter methylation (-), and suggested Lynch syndrome.ConclusionPatients with MSI-H colorectal cancers not fulfilling the Bethesda guidelines possibly have hereditary colorectal cancers. Adding tests of hMLH1 promoter methylation and BRAF mutations can be useful to distinguish them from sporadic colorectal cancers.

Familial risk-colorectal cancer: ESMO Clinical Practice Guidelines

J. Balmana1, F. Balaguer2, A. Cervantes3 & D. Arnold4, on behalf of the ESMO Guidelines Working Group* Department of Medical Oncology, Hospital Vall d’Hebron, Vall d’Hebron Institute of Oncology (VHIO), Universitat Autonoma de Barcelona, Barcelona; Department of Gastroenterology, Hospital Clinic, CIBERehd, IDIBAPS, University of Barcelona, Barcelona; Department of Hematology and Medical Oncology, INCLIVA, University of Valencia, Valencia, Spain; Department of Medical Oncology, Tumor Biology Clinic, Albert Ludwigs University, Freiburg, Germany;

A Family with Muir-Torre Syndrome

Purpose: Muir-Torre Syndrome (MTS) is a phenotypic subset of Lynch syndrome (LS) characterized by the presence of a sebaceous neoplasm with at least one visceral malignancy. Sebaceous neoplasms include adenomas, epitheliomas, carcinomas, and keratoacanthomas. Colorectal cancer (CRC) is the most common visceral tumour (50% of cases), followed by genitourinary cancers (25%). Other associated cancers include breast, lung, gastric, small intestine, and hematologic. A 42-year-old male with a family history of LS was referred to our care after a colonoscopy demonstrated a sessile polyp at the splenic flexure, found to be adenocarcinoma on histology. He underwent segmental colectomy and adjuvant chemotherapy. At follow-up, he gave a history of histologically-confirmed sebaceous adenomas. Given the diagnosis of CRC and history of sebaceous adenomas, a diagnosis of MTS was made. Detailed family history revealed that his mother and two siblings also met criteria for MTS. The patient's mother, who is known to have MSH2 mutation, had CRC at age 43, kidney and bladder cancers, and sebaceous adenomas. The patient's sister had CRC, endometrial cancer, and sebaceous adenomas. His brother had a history of sebaceous carcinoma at age 21. The patient underwent genetic testing, and was positive for the MSH2 mutation. MTS is inherited in an autosomal-dominant manner and exhibits a slight predominance in men, with initial malignancy occurring at a median age of 53 years. In general, sebaceous neoplasms are rare, and should raise suspicion of MTS. LS is caused by mutations in genes encoding for mismatch repair (MMR) proteins. These proteins ensure genomic stability by correcting single-base mismatches and insertiondeletion loops that form during DNA replication. Mutations in MMR genes also result in microsatellite instability (MSI). Testing for loss of MMR protein expression as well as presence of MSI forms the basis of screening tumors in patients suspected of having LS. The two most frequently affected MMR genes in LS and MTS are MSH2 and MLH1. In LS, the genes are equally implicated, but in MTS, 90% of cases have MSH2 mutations. Clinical diagnostic criteria for LS can be found in the revised Bethesda guidelines. Further MSI testing and germline mutation analysis is recommended if at least one of these criteria is met. MTS is a rare entity, and there are few reports in the literature describing multiple first degree relatives with the syndrome. There is need for increased familiarity with the diagnostic criteria for HNPCC, including recognition of sebaceous neoplasms as HNPCC-associated tumors, because of the early onset and high penetrance of cancer and the demonstrated effectiveness of screening for this condition.

Lynch syndrome–associated colorectal carcinoma: frequent involvement of the left colon and rectum and late-onset presentation supports a universal screening approach

The optimal strategy for screening patients with colorectal carcinoma for Lynch syndrome (LS) is a subject of continued debate in the literature with some advocating universal screening while others arguing for selective screening. We evaluated 1292 colorectal carcinomas for DNA mismatch repair protein abnormalities and identified 150 (11.6%) tumors demonstrating high-levels of microsatellite instability (MSI-H). MSI-H colorectal carcinomas were divided into sporadic (112/1292, 8.7%) and LS/probable LS-associated (38/1292, 2.9%) groups based on BRAF V600E mutation, MLH1 promoter hypermethylation, cancer history, and germline mismatch repair gene mutation. All MSI-H colorectal carcinomas were analyzed for grade, location, and tumor histology. The utility of the revised Bethesda guidelines and published predictive pathology models for MSI-H colorectal carcinomas (PREDICT and MSPath) were evaluated. Left-sided MSI-H colorectal carcinomas were more frequently associated with LS compared with right-sided MSI-H colorectal carcinomas (12/21, 57% versus 26/129, 20%, P = .0008). There was no significant difference in histology between sporadic MSI-H and LS/probable LS-associated colorectal carcinomas except for a slightly higher proportion of sporadic MSI-H tumors demonstrating tumor-infiltrating lymphocytes (81% versus 61%, P = .015). Neither pathology predictive model identified all LS-associated colorectal carcinomas (PREDICT: 33/38, 87%; MSPath: 35/38, 92%). 12/117 (10%) MSI-H colorectal carcinomas identified in patients >60 years were LS/probable LS-associated. Our results demonstrate that models of predicting MSI-H fail to identify LS-associated colorectal carcinoma given their reliance on right-sided location. A significant proportion (32%) of LS-associated colorectal carcinoma is identified in patients >60 years. Finally, our results demonstrate similar morphologic features between LS-associated and sporadic MSI-H colorectal carcinomas.

High incidence of large deletions in the PMS2 gene in Spanish Lynch syndrome families

Lynch syndrome (LS) is caused by germline mutations in one of the four mismatch repair (MMR) genes. Defects in this pathway lead to microsatellite instability (MSI) in DNA tumors, which constitutes the molecular hallmark of this disease. Selection of patients for genetic testing in LS is usually based on fulfillment of diagnostic clinical criteria (i.e. Amsterdam criteria or the revised Bethesda guidelines). However, following these criteria PMS2 mutations have probably been underestimated as their penetrances appear to be lower than those of the other MMR genes. The use of universal MMR study-based strategies, using MSI testing and immunohistochemical (IHC) staining, is being one proposed alternative. Besides, germline mutation detection in PMS2 is complicated by the presence of highly homologous pseudogenes. Nevertheless, specific amplification of PMS2 by long-range polymerase chain reaction (PCR) and the improvement of the analysis of large deletions/duplications by multiplex ligation-dependent probe amplification (MLPA) overcome this difficulty. By using both approaches, we analyzed 19 PMS2-suspected carriers who have been selected by clinical or universal strategies and found five large deletions and one frameshift mutation in PMS2 in six patients (31%). Owing to the high incidence of large deletions found in our cohort, we recommend MLPA analysis as the first-line method for searching germline mutations in PMS2.

Cancer risks and mutation spectrum of mismatch repair genes in African American families with Lynch syndrome.

1530 Background: Although African Americans (AA) have the highest colorectal cancer (CRC) incidence and mortality of all populations in the United States, no studies have determined cancer risk and mismatch repair (MMR) genes mutation spectrum in LS patients of AA ancestry and the contribution of this syndrome to cancer disparities. Thus, the aims of this study are: (1) to describe LS cancers in AAs; (2) to investigate the mismatch repair (MMR) gene mutation spectrum in AA families with LS; (3) to determine how Amsterdam II criteria, revised Bethesda guideline, and PREMM(1,2,6) model perform for predicting MMR gene mutations in this population. Methods: Pedigrees of AA families with deleterious mutation or suspected deleterious mutation in MMR genes from five US referral centers were analyzed for personal and familial clinical cancer histories. Results: Twenty-four AA families were identified, of which 22 had deleterious mutations (15 MLH1, 4 MSH2, 2 MSH6, 1 PMS2) and 2 had suspected deleterious mutations (1 MLH1, 1 MSH2). Three recurrent mutation were found in MLH1(677G&gt;A, IVS1-2A&gt;G, IVS4-1G&gt;A), accounting for 25% of all mutations. Of 24 probands, 58% were female and 96% had personal history of cancer. The median age at first primary tumor was 42yrs (range 28-57) and 50% developed more than 1 primary tumor. The majority of probands (79%) had CRC (median age of onset – 42yrs [range 31-61]), of which 26% had at least 2 CRC primaries. Endometrial cancer developed in 50% of the women (median age of onset – 51yrs [range 32-57]). Amsterdam II and Bethesda criteria were met in 63% and 88% of the individuals, respectively. Median score by PREMM(1,2,6) model was 54% (range 12.9-99.8). Conclusions: To our knowledge, this is the largest series of AA families with LS reported to date. Earlier age of onset for CRC at 42yrs (previously reported ~45 yrs) is suggested. The majority of mutations were found in MLH1 (67%), including three recurrent mutations. A 10% cutoff for PREMM(1,2,6) predictive model identified all mutation carriers. Larger studies are warranted to confirm the differences observed in age of CRC onset in this population.

Characterization of colorectal cancer (CRC) in Lynch syndrome (LS) patients with MSH6 or PMS2 mutations.

1555 Background: The majority of LS patients harbor germline mutations in the MLH1 or MSH2 genes. However, ~10% have MSH6 and ~&lt;5% PMS2 mutations. An attenuated form of LS has been suggested in MSH6/PMS2 carriers with decreased CRC risk and older age of disease onset. As recent guidelines suggest that initiation of CRC screening may be delayed in such patients, we characterized our patients with MSH6/PMS2-associated CRC. Methods: We obtained an IRB waiver to identify all LS patients with CRC, defined as the presence of a deleterious germline mutation in a MMR gene, from the Clinical Genetics database at MSKCC. Clinical, pathologic, and genetic features were extracted from medical records and Progeny software. Results: Of 147 LS patients with CRC, 23 had mutations in the MSH6 (n=16, 11%) or PMS2 (n=7, 5%) genes. Mean age at CRC diagnosis was 48.5 yrs (range 32-70) in MSH6 and 40.7 (range 22-57) in PMS2 carriers. 16 (70%) and 5 (22%) were diagnosed at age ≤50 or ≤35, respectively. 4 (17%) had metachronous and 3 (13%) synchronous primary CRCs, and 5 (22%) had additional LS-associated cancer. Although all 23 LS patients met Revised Bethesda guidelines, only 50% of MSH6 and 0 of the PMS2 carriers met Amsterdam I/II criteria (AC). Of 32 independent primary CRCs, 18 (56%) were stage I/II, 9 (28%) stage III, and 1 (3%) stage IV. 9/9 MSH6 and 4/4 PMS2 CRCs had high-frequency microsatellite instability. In MSH6 carriers, 11/13 had absence of MSH6protein expression only on IHC, 1 had inconclusive MSH6 staining, and 1 had absence of both MSH6 &amp; MSH2 proteins. In PMS2carriers, 7/7 had absence of PMS2 on IHC, 2 also had equivocal/focal MLH1 staining. Right-sided CRC was present in 50% and at least 40% had mucinous features. 26/29 (90%) of tumors underwent segmental resection. 6/11 stage II patients received adjuvant chemotherapy including 2 with pT4N0 tumors. With a mean follow-up of 5.6 yrs to date, 1 patient is known to have developed recurrent CRC. Conclusions: Although the majority of MSH6/PMS2 CRC patients do not meet AC, 70% of CRCs were diagnosed at age ≤50, 22% at age ≤35, and 30% had synchronous/metachronous CRCs. These findings have important implications for CRC surveillance and may not support delaying colonoscopy initiation in MSH6/PMS2 LS families.