Loss Of Mismatch Repair Expression Research Articles

BI09 Microsatellite instability and loss of mismatch repair proteins in nonmelanoma skin cancer and treatment-resistant phenotypically distinct precancerous lesions in Muir–Torre/Lynch syndrome: a multicentre retrospective study

Abstract DNA mismatch repair (MMR) gene mutations resulting in microsatellite instability (MSI) are associated in the pathogenesis of Muir–Torre syndrome (MTS), a variant of Lynch syndrome (LS). It is characteristically defined by the association of at least one sebaceous skin neoplasm and/or keratoacanthoma and a visceral malignancy. The presence of cutaneous lesions plays a vital role in the early detection and preventive cancer screening of the disease; however, nonmelanoma skin cancers (NMSCs) and their precursors are seldom reported. We conducted a retrospective multicentre study between 2011 and 2022 of adults with a confirmed genetic diagnosis of MTS/LS across two specialist institutions presenting with phenotypically distinct treatment-resistant precancerous skin lesions and/or NMSC with the associated loss of MMR expressions consistent with their germline mutations which are currently not recognized diagnostic features. Median age at the onset of precancerous/NMSC in eight individuals was 57.5 years, with an equal sex distribution. Lesions occurred mostly on the face (n = 14), followed by the forearms (n = 8), dorsum of the hands (n = 9), the legs (n = 4) and the chest (n = 1). Our study histologically and immunohistochemically examined MMR expressions and MSI in 20 precancerous and/or NMSCs. Loss of expression and MSI were found in actinic keratoses (AK) (n = 6/7), disseminated superficial actinic porokeratosis (DSAP; n = 1/2), squamous cell carcinoma (n = 4/5) and basal cell carcinoma (n = 4/4). Additionally, we found sebaceomas with atypia (n = 2/2). In 17 lesions, the loss of MMR expression and MSI were consistent with their germline mutations. We also discovered that all lesions identified with MSI had normal adjacent skin with no loss of MMR expression. Our observations suggest the detection of MSI, and MMR gene abnormality, play a critical role in the development of precancerous and NMSC other than sebaceous neoplasms in this disease. To date, the diagnostic criteria for MTS/LS do not include NMSC and their precursors, and these have rarely been reported. We note a clinically distinct presentation of widespread erythematous scaly lesions resembling AK/DSAP, resistant to multiple treatments, which is an additional recognizable clinical feature in this patient subgroup. This is an important association in cancer-prone individuals and immunohistochemistry testing for MMR genes should be encouraged. This can be a powerful investigative tool as AK/DSAP are easily identifiable, numerous and readily accessible for DNA analysis; therefore, detecting the presence of MSI in the skin may aid in screening individuals promptly. MTS/LS is best managed by a multidisciplinary team with close surveillance for visceral malignancies, highlighting the importance of routine monitoring for precancerous and nonsebaceous skin cancers.

Universal screening for Lynch syndrome in operated colorectal cancer by immunohistochemistry: a cohort of patients in Liaoning province, China.

Lynch syndrome (LS) is the most common hereditary colorectal cancer syndrome worldwide. Due to the decreasing family size in Liaoning province. The Bethesda and Amsterdam II criteria have lower sensitivity and specificity and are not suitable for the local population. Immunohistochemistry screening for mutations in DNA mismatch repair (MMR) in newly diagnosed colorectal cancer can improve the detection rate of LS. All newly diagnosed colorectal cancer patients who underwent surgery between January 2018 and June 2020 at Cancer Hospital of China Medical University and Shengjing Hospital of China Medical University from Liaoning China were included retrospectively, and the ratio of universal LS screening by immunohistochemistry, MMR protein deficiency (dMMR) ratio, MLH1 loss, MSH2 loss, MSH6 loss, and PMS2 loss was analyzed. The clinicopathological characteristics of patients with pMMR and dMMR were analyzed. A total of 7019 colorectal cancer patients underwent surgery and 4802 (68.41%) patients were screened by immunohistochemistry for MMR, 258 (5.37%) cases were reported to have a loss of MMR expression. In the dMMR group, a higher number of patients were under 50 years old, more tumors were located at the right colon, less patients have lymph node metastasis, more tumors were stage II, and histological types of mucinous carcinoma or signet ring carcinoma were more common, compared with the pMMR group. Only 2.71% dMMR patients meet Amsterdam criteria II, 2.71% of patients meet Revised Bethesda guidelines, and 17.83% meet Chinese LS criteria. Twenty-five dMMR patients were confirmed by next-generation sequencing and five families were confirmed as Lynch family. These data imply that universal screening for LS by immunohistochemistry may be effective in Liaoning province.

Sarcomatous Transformation in Undifferentiated/Dedifferentiated Endometrial Carcinoma: An Underrecognized Phenomenon and Diagnostic Pitfall

Undifferentiated/dedifferentiated carcinoma is an aggressive endometrial carcinoma which remains underrecognized but may account for up to 9% of all endometrial malignancies. We describe 3 cases in which the undifferentiated component was associated with sarcomatous differentiation, characterized by spindled cells in 2 cases and heterologous malignant cartilage in 1 case. Two of the 3 cases demonstrated mismatch repair deficiency by immunohistochemistry. This phenomenon has not previously been formally reported and increases the likelihood of misdiagnosis, especially within biopsy samples; differential diagnoses may include endometrial stromal sarcoma and grade 3 endometrioid adenocarcinoma with spindled morphology. We review the current literature and provide strategies for resolving the differential diagnoses, with a suggested panel of antibodies which includes EMA, E-cadherin, and mismatch repair proteins as approximately 50% of cases show loss of mismatch repair expression.

B21 - Mismatch repair protein expression and inflammation in human pancreatic cancer

Background: DNA mismatch repair (MMR) system maintains genomic stability and mediates cellular response to DNA damage. Recent studies have shown that a subset of MMR deficient pancreatic ductal adenocarcinoma (PDAC) may represent promising candidates for immunotherapy. Inflammation can promote PDAC development and progression, with a key role played by cytokines, such as IL-6, and cyclooxygenase-2 (COX-2). Studies on other gastrointestinal malignancies have demonstrated a link between IL-6 and loss of MMR expression. In this study we analyzed the correlation between MMR protein expression and inflammation markers in PDAC. Methods: Tissue samples from 91 resected PDAC patientswere subjected to immunohistochemical staining to assess the expression of MLH1, MSH2 and MSH6. Stromal and tumoral IL-6 levels and COX-2 expression were also assessed with immunohistochemistry. Expression of MMR proteins was correlated with IL-6 and COX-2 expression by chi-square test. Results: At immunohistochemistry analysis, 42.2% of samples were negative for MLH1 expression, while 27.7% were negative for MSH2 and 34.4% for MSH6. Nineteen patients (20.9%) presented loss of at least two MMR proteins. Stromal and tumoral IL-6 was expressed in 55.6% and 44.4% of samples, respectively, while COX-2 was found in 62.5% of samples. MMR protein expression was not related to clinical characteristics, as pathological stage or grading, or to clinical outcome in terms of overall survival (OS). MMR deficiency, defined as loss of at least one of the three MMR protein analysed, significantly correlated with expression of stromal IL-6 (p= 0.005). Moreover, we showed a significant correlation between MMR deficiency and high expression of both inflammation markers (p= 0.0009) with 69.5% of MMR deficient tumors with expression of both IL-6 and COX-2. Conclusions: Our results suggest that MMR deficiency and inflammation are correlated in human PDAC pathogenesis, confirming what observed in other gastrointestinal tumors. These results give new insights on the role of inflammation in PDAC and should be considered in the selection of patients for future development of immunotherapies in PDAC.

Clinical and Pathologic Features of Hispanic Endometrial Cancer Patients With Loss of Mismatch Repair Expression.

Approximately 3% to 5% of endometrial cancers (EC) are associated with Lynch syndrome (LS). The clinical characteristics and prevalence of LS have not been well studied in the US Hispanic population. Hispanics are the largest and fastest growing ethnic minority group in the United States. We sought to characterize the demographics, tumor characteristics, and prevalence of loss of mismatch repair (MMR) protein expression in a large Hispanic population with EC. From January 1, 2005, to August 1, 2012, 83 women of Hispanic ethnicity diagnosed with EC 50 years and younger were identified. Clinical and pathologic data were abstracted from the electronic medical record. Tumor studies included immunohistochemistry of MLH1, MSH2, MSH6, and PMS2 and methylation of the MLH1 promoter. Ninety-five percent of patients were overweight or obese. The mean body mass index was 40.1 kg/m, 75% had irregular menses, 36% had diabetes, 46% were nulliparous, and 95% had endometrioid histology. Thirteen patients (15.7%) had tumor MMR deficiency due to a presumed germline mutation (9 MSH6, 3 MSH2, and 1 MLH1). The pattern of MMR protein loss was consistent with the expected binding properties of the MMR heterodimer complexes. No significant difference was found in clinical or pathological variables between patients with and without MMR deficient tumors. The prevalence of molecular findings consistent with LS was at least as high as other populations of varied geography, race, and ethnicity. We found no reliable factors to include body mass index, family history, synchronous tumors, or pathologic tumor features to serve as triage markers for which ECs should be screened for MMR protein loss. Our findings support a recommendation for universal screening of ECs utilizing 2-antibody testing with MLH1 promoter methylation testing as indicated up to 60 years or older. Our recommendations should be generalizable to other Hispanic populations in the Southern United States.

Molecular pathogenesis of endometrial intraepithelial neoplasia: Precursor to endometrial carcinoma

Objectives: To characterize the relationship between DNA mismatch repair (MMR), ARID1A, and PTEN in endometrial intraepithelial neoplasia (EIN).Methods: Type 1 endometrial carcinoma typically develops from a precursor lesion, endometrial hyperplasia, or EIN. The DNA MMR system prevents tumor progression by correcting errors that occur during DNA replication and is present in a proportion of endometrial cancers. Tumor suppressor genes ARID1A and PTEN are also implicated in the molecular pathogenesis of endometrial carcinoma. Previous studies have shown that in endometrial carcinoma, MMR deficiency may be associated with ARID1A mutations. However, in EIN, the relationship between loss of expression (LOE) of MMR, ARID1A, and PTEN has yet to be established.In a retrospective review, we identified 113 patients with EIN on endometrial biopsy from 2009 to 2014. Tissue microarray blocks were evaluated with immunohistochemical stains using antibodies against MLH1, PMS2, MSH2, MSH6, ARID1A, and PTEN. Statistical analyses were performed, with a P < .05 considered statistically significant.Results: In EIN, rates of LOE of MMR, ARID1A, and PTEN were 4.4% (n = 5), 6.2% (n = 7), and 50.4% (n = 57), respectively. Loss of MMR expression was not significantly associated with expression of ARID1A (P = 1.000) or PTEN (P = .2062). Development of a subsequent invasive malignancy was not significantly associated with LOE of ARID1A (P = .1135), DNA MMR (P = .2424), or PTEN (P = .1670). When combined, LOE of ARID1A and MMR was significantly associated with subsequent cancer (P = .0109).Conclusions: In this series of EIN, the frequency of PTEN LOE (50.4%) agreed with that seen in previous studies. Unlike rates demonstrated in endometrial carcinoma, the proportion of LOE in MMR (4.4%) and ARID1A (6.2%) seen in the precursor lesion were relatively low and thus seem to be nonessential in the development of EIN. There were no cases of concordant LOE of MMR and ARID1A, suggesting independent pathways or differences in temporal patterns in gene expression during the premalignant phase. When combined, LOE of ARID1A and MMR was significantly associated with the development of a subsequent malignancy, suggesting potential prognostic markers, which will require further evaluation. Objectives: To characterize the relationship between DNA mismatch repair (MMR), ARID1A, and PTEN in endometrial intraepithelial neoplasia (EIN). Methods: Type 1 endometrial carcinoma typically develops from a precursor lesion, endometrial hyperplasia, or EIN. The DNA MMR system prevents tumor progression by correcting errors that occur during DNA replication and is present in a proportion of endometrial cancers. Tumor suppressor genes ARID1A and PTEN are also implicated in the molecular pathogenesis of endometrial carcinoma. Previous studies have shown that in endometrial carcinoma, MMR deficiency may be associated with ARID1A mutations. However, in EIN, the relationship between loss of expression (LOE) of MMR, ARID1A, and PTEN has yet to be established. In a retrospective review, we identified 113 patients with EIN on endometrial biopsy from 2009 to 2014. Tissue microarray blocks were evaluated with immunohistochemical stains using antibodies against MLH1, PMS2, MSH2, MSH6, ARID1A, and PTEN. Statistical analyses were performed, with a P < .05 considered statistically significant. Results: In EIN, rates of LOE of MMR, ARID1A, and PTEN were 4.4% (n = 5), 6.2% (n = 7), and 50.4% (n = 57), respectively. Loss of MMR expression was not significantly associated with expression of ARID1A (P = 1.000) or PTEN (P = .2062). Development of a subsequent invasive malignancy was not significantly associated with LOE of ARID1A (P = .1135), DNA MMR (P = .2424), or PTEN (P = .1670). When combined, LOE of ARID1A and MMR was significantly associated with subsequent cancer (P = .0109). Conclusions: In this series of EIN, the frequency of PTEN LOE (50.4%) agreed with that seen in previous studies. Unlike rates demonstrated in endometrial carcinoma, the proportion of LOE in MMR (4.4%) and ARID1A (6.2%) seen in the precursor lesion were relatively low and thus seem to be nonessential in the development of EIN. There were no cases of concordant LOE of MMR and ARID1A, suggesting independent pathways or differences in temporal patterns in gene expression during the premalignant phase. When combined, LOE of ARID1A and MMR was significantly associated with the development of a subsequent malignancy, suggesting potential prognostic markers, which will require further evaluation.

Abstract 1285: Identification of MMR gene exonic rearrangements in suspected Lynch syndrome tumors without loss of MMR expression

Abstract Lynch syndrome (LS), also called Hereditary Non-Polyposis Colorectal Cancer, the most well studied form of familial CRC, is responsible for about 3% of all CRC cases. LS-associated CRC often exhibits one or more of the following features namely early age of onset, occurrence of synchronous/metachronous tumors, presence of more than one affected family member and tumors predominantly localized to the proximal/right colon with specific clinico-pathological features such as a mucinous histology, poor differentiation and immune infiltration. LS is primarily a disease of defective MisMatch Repair (MMR) and is caused by germline mutational inactivation of any one of four major MMR genes viz. MLH1, MSH2, MSH6 and PMS2. A hallmark of LS-associated tumors is presence of ‘microsatellite instability’ (MSI), a term used to describe frequent occurrence of expanded/contracted microsatellites that arise during DNA replication and are not corrected due to defective MMR. MLH1 and MSH2 account for a majority (up to 90%) of LS cases while MSH6 and PMS2 are involved in a minor proportion. Mutational inactivation of an MMR gene almost always results in loss of corresponding protein expression in the tumor, which can be easily detected by immunohistochemistry. In the first comprehensive study from India, we analyzed MSI and determined expression status of the four MMR genes in forty eight suspected LS-associated colorectal tumor samples. Though a majority (85.4%) exhibited MSI, only 58% exhibited loss of MMR expression, a significantly low proportion compared to reports from other populations. PCR-DNA sequencing and Multiple Ligation-dependent Probe Amplification based mutation and exonic deletion/duplication screening respectively, revealed MMR gene lesions in 81% of samples exhibiting loss of corresponding MMR protein expression, including thirteen mutations and four exonic rearrangements. Seven novel mutations (four in MLH1 and three in MSH2) were identified. Surprisingly, MMR gene lesions were also detected in a significant proportion (78%) of tumor samples not exhibiting MMR expression loss. Interestingly, samples with and without MMR expression exhibited significant differences with respect to mucinous histology and instability exhibited by specific microsatellites. In addition, MMR negative samples mainly harbored MMR gene in-del or point mutations while MMR positive samples predominantly harbored MMR gene exonic rearrangements. The study has therefore revealed for the first time a significant proportion of suspected LS tumors not exhibiting loss of MMR expression despite harboring MMR gene rearrangements. More importantly, our results indicate significant differences in the biology of LS-associated colorectal tumors occurring due to missense/in-del mutations in MMR genes causing loss of expression and those that occur due to MMR gene exonic rearrangements not resulting in loss of expression. Citation Format: Murali D. Bashyam, Viswakalyan Kotapalli, Ratheesh Raman, Brijesh K. Yadav, Ajay K. Chaudhary, Swarnalata Gowrishankar, Shantveer G. Uppin, Ravikanth Kongara, Regulagadda A. Sastry, Mohana Vamsy, Sujit Patnaik, Shoba Dsouza, Devendra C. Desai, Tester Ashavaid. Identification of MMR gene exonic rearrangements in suspected Lynch syndrome tumors without loss of MMR expression. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1285. doi:10.1158/1538-7445.AM2014-1285

Abstract 4854: DNA mismatch repair deficiency in sebaceous skin tumors: a large case series from a single pathology practice.

Abstract Muir Torre syndrome is characterized by the presence of sebaceous skin tumours and/or multiple keratoacanthomas, as well as a personal or family history of internal malignancies. It is now recognized that many of these families are a phenotypic variant of Lynch syndrome in which there is an inherited genetic defect in one of the DNA mismatch repair (MMR) genes (MLH1, MSH2, MSH6 or PMS2), and that mutation carriers may be identified through testing sebaceous skin tumours for loss of protein expression. In many cases, however, loss of MMR expression in skin tumours may be sporadic in nature, and further study is required to determine whether clinicopathological features or other tumor molecular changes can refine the process of triaging patients for expensive genetic testing for Lynch syndrome. The aim of this retrospective study was to assess the results of reflex immunohistochemical screening of sebaceous skin tumours in order to identify associations between clinicopathological features of these tumours including subtypes, tumor location, and specific protein(s) showing loss of expression.An audit of sebaceous tumours tested by Immunohistochemistry (IHC) for MMR expression identified 428 individuals (149 females, 279 males) with one or more lesions tested between January 2009 and April 2012, at Sullivan Nicolaides Pathology. Patients’ ages ranged from 17 to 100 years. A total of 450 skin lesions were examined: 232 sebaceous adenomas, 66 sebaceous carcinomas, 82 sebaceomas, 27 sebaceous hyperplasias, 12 sebaceous tumours NOS, as well as 14 squamous cell and 13 basal cell carcinomas with sebaceous differentiation, and 4 keratoacanthomas. Excluding unclassified sebaceous tumours, MMR deficiency was detected in a total of 129/438 (29%) lesions. Of the MMR deficient tumours 97 showed loss of MSH2 and MSH6 (75%), with MLH1/PMS2 loss observed in 21 (16%) cases, solitary MSH6 loss in 10 (8%), and PMS2 loss alone in one (1%). No statistical association was found between MMR deficiency and gender (81/279 (29%) males; 37/149 (25%) females), or patient age (68 yr MMR deficient vs. 65 yr MMR normal). The majority of tumours were located on the head and neck (366/447: 82%), while 52 (12%) were on the trunk and 19 (4%) on the limbs. While most MMR deficient tumours were located on the head and neck (84/366; 23%), MMR loss of expression was more commonly observed in lesions on the trunk (36/62; 58%) and limbs (9/19; 47%), and MLH1/PMS2 and MSH6 only losses were proportionally more common in non-head and neck sites. MMR loss was most commonly observed in sebaceous adenomas (84/232: 36%) and sebaceomas (22/82: 27%), and less frequently in other sebaceous lesions. We have identified MMR deficiency in a significant number of sebaceous skin lesions, yet it remains unclear from the current data what proportion of these patients have a germline mutation in an MMR gene and thus have Muir Torre (Lynch) syndrome. Citation Format: Michael D. Walsh, Rhonda J. Edwards, Kevin J. Whitehead, Michael R. Gattas, Daniel D. Buchanan. DNA mismatch repair deficiency in sebaceous skin tumors: a large case series from a single pathology practice. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4854. doi:10.1158/1538-7445.AM2013-4854

Survival of endometrial cancer patients with lymphatic invasion and deficient mismatch repair expression

ObjectiveThis study examines patients under the age of 70 with endometrial cancer and lymphatic invasion or lymph node metastases. Survival of patients with loss of tumor mismatch repair expression is compared to survival of patients with normal mismatch repair expression. MethodsThis is a retrospective review of patients treated from 1998–2009 for carcinoma of the endometrium. All patients with lymphatic invasion, including lymph node metastases, had immunohistochemical staining of the primary tumor for loss of expression of the mismatch repair genes MLH1, PMS2, MSH6, and MSH2. Overall survival and disease specific survival were compared using Kaplan–Meier plots. ResultsSixty-six patients were identified for inclusion; 26 demonstrated loss of mismatch repair expression and 40 demonstrated normal mismatch repair expression. Overall survival and disease specific survival were significantly better in the group with defective mismatch repair expression. Subgroup analysis of FIGO stage 3C patients also showed significantly better survival in patients with deficient mismatch repair expression. ConclusionFor patients with endometrial cancer and lymphatic invasion, patients demonstrating loss of mismatch repair expression in the primary tumor appear to have a significantly better survival than patients with normal mismatch repair expression. Further investigation appears warranted to examine a possible role of mismatch repair expression as a prognostic marker for high risk patients with endometrial cancer.

Clinical and pathologic features of young endometrial cancer patients with loss of mismatch repair expression

ObjectiveThis study examines premenopausal and early menopause patients in a unique population with endometrial cancer and loss of mismatch repair (MMR) gene expression. The purpose is to compare clinical and pathologic differences in patients with loss of expression (LOE) to those with normal expression (NE). MethodsEndometrial cancer patients under age 60 in-between 1998 and 2008 were identified from a single tumor registry. Clinical and pathologic data were abstracted from records. Staining for expression of MSH6, MSH2, MLH1, and PMS2 were performed on archived tissue blocks. Statistical analysis was performed. Results158 patients were analyzed; 58% Asian, 34% Pacific Islander, and 8% Caucasian. 31 demonstrated LOE of at least one MMR gene; 127 retained NE. 50% Caucasian, 21.9% Asian, and 12.5% Pacific Island populations had LOE of one or more MMR genes. LOE was found to have a higher incidence of Grade III (p=0.0013) and stage 3–4 tumors (p=0.0079), mean depth of myometrial invasion (p=0.0019), lymphovascular space invasion (p=0.0020), nodal metastases (p=0.0157), and a lower incidence of Grade I (p=0.0020) and stage 1A tumors (p=0.0085). LOE had a significantly lower mean BMI (p=0.0001). 35% of patients in the NE vs zero in the LOE group had a BMI greater than 40. ConclusionYounger patients with LOE endometrial cancer appear to represent a clinically significant subgroup of patients without features characteristically found in classic type 1 endometrial cancer generally demonstrating lower BMI and tumors associated with poor prognostic characteristics. It is unclear if the distinctive ethnicity found in Hawaii has a significant impact on outcome. Further investigation is necessary to identify appropriate treatment strategies.

Immunohistochemical testing of conventional adenomas for loss of expression of mismatch repair proteins in Lynch syndrome mutation carriers: a case series from the Australasian site of the colon cancer family registry

AbstractDebate continues as to the usefulness of assessing adenomas for loss of mismatch repair protein expression to identify individuals with suspected Lynch syndrome. We tested 109 polyps from 69 proven mutation carriers (35 females and 34 males) belonging to 49 Lynch syndrome families. All polyps were tested by immunohistochemistry for four mismatch repair proteins MLH1, MSH2, MSH6 and PMS2. Detailed pathology review was performed by specialist gastrointestinal pathologists. The majority of polyps (86%) were conventional adenomas (n=94), with 65 tubular and 28 tubulovillous adenomas and a single villous adenoma. The remaining 15 lesions (14%) were serrated polyps. Overall, loss of mismatch repair expression was noted for 78/109 (72%) of polyps. Loss of mismatch repair expression was seen in 74 of 94 (79%) conventional adenomas, and 4 of 15 (27%) serrated polyps from mismatch repair gene mutation carriers. In all instances, loss of expression was consistent with the underlying germline mutation. Mismatch repair protein expression was lost in 27 of 29 adenomas with a villous component compared with 47 of 65 adenomas without this feature (93 vs 73%; P=0.028). A strong trend was observed for high-grade dysplasia. Mismatch repair deficiency was observed in 12 of 12 conventional adenomas with high-grade dysplasia compared with 60 of 79 with low-grade dysplasia (100 vs 76%; P=0.065). We were unable to demonstrate a significant association between conventional adenoma size or site and mismatch repair deficiency. All (4/4 or 100%) of the serrated polyps demonstrating mismatch repair deficiency were traditional serrated adenomas from a single family. Diagnostic testing of adenomas in suspected Lynch syndrome families is a useful alternative in cases where cancers are unavailable. The overwhelming majority of conventional adenomas from mutation carriers show loss of mismatch repair protein expression concordant with the underlying germline mutation.

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

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

Identification and Management of Lynch Syndrome

The Lynch syndrome, (also as hereditary nonpolyposis colorectal cancer) is an autosomal dominant disease, caused by germline mutations in four mismatch repair (MMR) genes (MSH2, MLH1, PMS2, and MSH6), most notably MLH1 or MSH2, Tumors caused by loss of mismatch repair gene function exhibit frequent errors in microsatellite DNA, short segments of DNA containing 1~6 repeats of nucleotides, and are thus said to exhibit microsatellite instability (MSI). Ninety percent of colon cancers associated with Lynch syndrome show MSI, while only 15% sporadic CRCs have MSI, caused mainly by hypermethylation of MLH1 promoter. Unlike familial adenomatous polyposis, clinical features of the Lynch syndrome are not so unique. However, the Lynch syndrome could be suspected at a relatively early age at onset of CRC, on account of a higher incidence of synchronous and metachronous CRCs, a predilection for the proximal colon, and specific pathologic findings including tumor-infiltrating lymphocytes, signet ring cells, or a strong mucinous component. Although the Lynch syndrome accounts for only 2 to 5% of all colorectal cancer patients, the identification of this syndrome is clinically relevant. Aggressive surveillance including colonoscopy for patients with Lynch syndrome and their relatives could prevent cancer development and reduce mortality. Currently, patients fulfilling the Amsterdam II/Revised Bethesda criteria are suggested to receive MSI and/or IHC analysis of the tumor. Mutation analysis should be offered in those with evidence of MSI or loss of MMR expression.

Sampling Strategies for Tissue Microarrays to Evaluate Biomarkers in Ovarian Cancer

Tissue microarrays (TMA) enable rapid analysis of biomarkers in large-scale studies involving archival tumor specimens, however, their utility in heterogeneous tumors such as ovarian cancer is limited. In this study, immunohistochemical analysis was done on TMAs comprised of epithelial ovarian cancer (EOC) to estimate the prevalence of loss of expression of three mismatch repair proteins. TMAs were initially created using cores sampled from the center of donor tissue blocks from 59 EOC cases. Full sections were subsequently created and levels of expression were compared between tissues sampled from the central portion versus the periphery. Follow-up analyses were done by obtaining cores from the periphery of up to five additional donor blocks per case. A linear mixed model for each protein was used to investigate differences between results from the initial and follow-up blocks. In the original TMAs created using centrally sampled cores, loss of mismatch repair expression was noted in 17 (29%) of the 59 cases. By comparison, analyses from peripherally sampled cores revealed loss of expression in only 6 of these 17 cases. For each protein, significant differences (P < 0.05) were detected between results from the initial donor block and the majority of the follow-up blocks. Our investigations, based on EOC, suggest that sampling variability in protein expression may result when TMAs are used. Thus, at least for EOC, it is important to preferentially sample from the periphery of tumor blocks where exposure to tissue fixatives is optimal.

Altered DNA Mismatch Repair Expression in Synchronous and Metachronous Colorectal Cancers

It is not clear what proportion of synchronous or metachronous colorectal cancers (CRCs) are associated with DNA mismatch repair (MMR) alterations or unsuspected Lynch syndrome. On the basis of tissue analyses, the aims were to evaluate DNA MMR expression in metachronous, synchronous, and isolated sporadic CRCs and to assess within-patient concordance of MMR expression in metachronous and synchronous CRCs. Tissue was evaluated from 34 patients with metachronous CRC, 34 matched solitary CRC patients, and 40 patients with synchronous CRCs. Subjects with known hereditary CRC were excluded. Immunohistochemical staining for MLH1 and MSH2 was performed on all tissues. Absent MLH1 or MSH2 staining of the initial metachronous tumor was observed in 27% compared with 21% of control CRCs, P = .58. The odds of metachronicity with absent immunostaining were 1.33 (95% confidence interval, 0.46-3.84). Loss of MMR expression was observed in at least one cancer in 30% of patients with synchronous CRC. MMR expression loss was discordant in 70% of metachronous CRCs and 50% of synchronous CRCs. Lynch syndrome was subsequently diagnosed in 2 patients with synchronous CRCs, both with concordant tumor MMR loss but in no patient with metachronous CRC. Among those without known Lynch syndrome, development of multiple primary CRCs appears to be due largely to somatic events and often occurs via different molecular pathways within the same patient. Altered MMR expression in sporadic CRC has low predictive value for metachronicity. MMR expression analysis in cases of multiple primary CRC might identify a small number of patients with unsuspected Lynch syndrome.