Accurate Distinction of Ovarian Clear Cell From Endometrioid Carcinoma Requires Integration of Phenotype, Immunohistochemical Predictions, and Genotype: Implications for Lynch Syndrome Screening.

Ovarian clear cell carcinoma (OCCC) and ovarian endometrioid carcinoma (OEC) are both associated with endometriosis but differ in histologic phenotype, biomarker profile, and survival. Our objectives were to refine immunohistochemical (IHC) panels that help distinguish the histotypes and reassess the prevalence of mismatch repair deficiency (MMRd) in immunohistochemically confirmed OCCC. We selected 8 candidate IHC markers to develop first-line and second-line panels in a training set of 344 OCCC/OEC cases. Interobserver reproducibility of histotype diagnosis was assessed in an independent testing cohort of 100 OCC/OEC initially without and subsequently with IHC. The prevalence of MMRd was evaluated using the testing cohort and an expansion set of 844 ovarian carcinomas. The 2 prototypical combinations (OCCC: Napsin A+/HNF1B diffusely+/PR-; OEC: Napsin A-/HNF1B nondiffuse/PR+) occurred in 75% of cases and were 100% specific. A second-line panel (ELAPOR1, AMACR, CDX2) predicted the remaining cases with 83% accuracy. Integration of IHC improved interobserver reproducibility (κ=0.778 vs. 0.882, P<0.0001). The prevalence of MMRd was highest in OEC (11.5%, 44/383), lower in OCCC (1.7%, 5/297), and high-grade serous carcinomas (0.7%, 5/699), and absent in mucinous (0/126) and low-grade serous carcinomas (0/50). All 5 MMRd OCCC were probable Lynch syndrome cases with prototypical IHC profile but ambiguous morphologic features: 3/5 with microcystic architecture and 2/5 with intratumoral stromal inflammation. Integration of first-line and second-line IHC panels increases diagnostic precision and enhances prognostication and triaging for predisposing/predictive molecular biomarker testing. Our data support universal Lynch syndrome screening in all patients with OEC when the diagnosis of other histotypes has been vigorously excluded.

Compliance with mismatch repair testing in pT1 colorectal cancer diagnosed before the age of 70 years.

Mismatch repair (MMR) testing is recommended in the Netherlands for all patients under 70 years of age with newly diagnosed colorectal cancer (CRC) in order to identify Lynch syndrome. T1 CRC can be removed by local excision or oncological surgical resection. We evaluated the frequency of MMR testing in pT1 lesions within the Dutch CRC screening cohort. pT1 CRC diagnosed within the Dutch population-based screening program from 2016-2018 were identified by the Dutch pathology registry (PALGA). Pathology reports were evaluated, including registration of MMR testing (by immunohistochemistry and/or microsatellite instability PCR). Frequency of MMR testing was compared between pT1 tumors that were treated by local (endoscopic or transanal) excision and oncological surgical resections. A total of 3.692 pT1 CRCs were diagnosed (median age 63 years, 61.4% males). MMR testing was performed in 83% and uptake increased over time (71% in 2016 to 92% in 2018, p<0.01). MMR testing was significantly more often performed in younger patients and in academic hospitals. When pT1 CRC was treated by oncological surgical resection (n=1.132), MMR testing was performed in 89% of cases and was known prior to oncological resection in 51% of cases. MMR testing occurred significantly less often in case of local excision (80% of n=2.560) compared to oncological surgical resection (p<0.01). MMR testing was performed in 83% of T1 CRCs and uptake increased over time. MMR testing was more frequently performed in pT1 CRC resected by oncological surgical resection compared with local excision.

Minimal microsatellite shift in microsatellite instability high endometrial cancer: a significant pitfall in diagnostic interpretation.

Mismatch-repair deficiency testing plays a critical role in the identification of proband in Lynch Syndrome families and triaging patients with high stage or recurrent solid malignancies for check point inhibitor (Pembrolizumab) immunotherapy. We compared microsatellite shift patterns of microsatellite instability PCR analysis at 5 NCI recommended loci between microsatellite instability high endometrial carcinoma (n = 50) and microsatellite instability high colorectal cancer (n = 19). The endometrial cancer cohort included 45 endometrioid, 1 serous, and 4 clear cell carcinomas. Overall, 52% (26/50) of microsatellite instability high endometrial cancers showed minimal microsatellite shift (defined as a one to three nucleotide repeat shift at an involved locus) observed at least at one locus. Among microsatellite instability high endometrial cancers with minimal microsatellite shift, the frequencies at each involved locus were D2S123 (21/21, 100%), D17S250 (10/11, 89%), D5S346 (11/12, 92%), BAT25 (9/12, 80%), and BAT26 (8/21, 45%). Noticeably, 11 of the 26 cases (42%) showed only minimal shift. Among microsatellite instability high endometrial cancers with minimal microsatellite shift, 65% (17/26) had combined MLH1 and PMS2 loss, 8% (2/26) had combined MSH2 and MSH6 loss, 13% (3/26) had MSH6 loss and 15% (4/26) had loss of PMS2 by immunohistochemistry. In contrast, only 16% (3/19) had minimal microsatellite shift seen in colorectal cancer cohort with corresponding loss of MLH1/PMS2, MSH2/MSH6, or MSH6. Overall, 15% (7/50) of microsatellite instability high endometrial carcinomas showed isolated loss of MSH6 in contrast to 7% (1/15) seen in microsatellite instability high colorectal carcinomas. In conclusion, microsatellite instability high endometrial carcinomas have a significantly higher frequency of minimal microsatellite shift that coincides with a high percentage of combined loss of MLH1/PMS2. Microsatellite instability high endometrial cancers also have more frequent loss of MSH-6. Diagnostically, recognition of minimal microsatellite shift is crucial for accurate interpretation of microsatellite instability PCR data of endometrial carcinoma.

Success of referral to genetic counseling after positive lynch syndrome screening test.

PURPOSE: Lynch syndrome (LS) is a hereditary condition that increases one's risk of developing colorectal, endometrial, and other extracolonic cancers. MD Anderson Cancer Center at Cooper implemented a reflex screening protocol for DNA mismatch repair (dMMR) deficiency. Those with findings suspicious for LS were referred for genetic counseling (GC). Our goal was to assess compliance with GC and factors associated with successful follow-up. METHODS: Immunohistochemistry (IHC) for the MMR proteins MSH2, MLH1, MSH6, and PMS2 was performed on all colorectal tumor resections from patients ≤70 years old and all stage II cancers. Tumors with loss of MLH1/PMS2 were subsequently tested for BRAF mutation or MLH1 promoter methylation to identify tumors with likely epigenetic inactivation of MLH1. Patients with loss of MLH1/PMS2 without BRAF mutations or with absence of MLH1 promoter methylation and those with loss of MSH2/MSH6 were referred to GC. Compliance with GC was assessed. RESULTS: Between March 2014 and August 2016, 203 tumors were tested by IHC. Fifteen (7.4%) patients had abnormal MMR protein expression patterns in the absence of BRAF mutation or MLH1 promoter methylation suggestive of possible LS. GC compliance was 35.7% overall and 85.7% in those with family history of LS-associated cancers. CONCLUSIONS: Overall, GC compliance was relatively low in our study. Interestingly, patients with a strong family history of LS-associated neoplasms were more likely to pursue GC. In the future, assessing and addressing barriers to seeking GC will provide opportunities to improve patient care through increased identification of patients with cancer predisposition syndromes.

Neoadjuvant therapy in microsatellite-stable colorectal carcinoma induces concomitant loss of MSH6 and Ki-67 expression.

Universal screening using immunohistochemistry for DNA mismatch-repair proteins (MLH1, MSH2, MSH6, and PMS2) is advocated by major professional medical organizations to identify Lynch syndrome-associated colorectal carcinoma. Loss of MSH6 expression independent of MSH2 expression has been reported in microsatellite-stable (MSS) colorectal carcinoma after neoadjuvant therapy. The mechanism remains unclear. We studied the immunohistochemical expression of MSH2, MSH6, and Ki-67 in MSS colorectal carcinoma with (n=50) or without (n=64) preoperative neoadjuvant therapy and Lynch syndrome-associated colorectal carcinoma with confirmed MSH6 germline mutation (n=3). Twelve of 50 MSS colorectal carcinoma postneoadjuvant resections demonstrated reduced MSH6 expression, with loss of expression ranging from 20% to 100% of tumor cells. Eight of 64 MSS colorectal carcinomas without neoadjuvant therapy also exhibited reduced MSH6 expression but to a lesser degree (10%-50% of tumor cells with loss of expression). In both subgroups, concomitant loss of MSH6 and Ki-67 expressions was demonstrated in the same tumor areas in consecutive tissue sections. However, 3 cases of Lynch syndrome-associated colorectal carcinoma due to germline MSH6 mutation revealed complete loss of MSH6 expression with discordant positive Ki-67 staining in the tumor cells. The MSH2-independent, Ki-67-related expression of MSH6 in colorectal carcinoma helps to explain the heterogeneous MSH6 staining in MSS colorectal carcinoma with or without neoadjuvant therapy.

Heterogenous MSH6 loss is a result of microsatellite instability within MSH6 and occurs in sporadic and hereditary colorectal and endometrial carcinomas.

Mismatch-repair (MMR) immunohistochemistry is used to detect tumor MMR deficiency associated with high-level microsatellite instability (MSI). Rare tumors show heterogenous loss of mutS homolog 6 (MSH6) with immunohistochemistry, defined by areas of retained staining and separate areas of complete loss of staining. To investigate the clinical interpretation of this phenomenon, we identified 22 cases of heterogenous MSH6 loss interpreted at Mayo Clinic from January 2001 through December 2012 and reviewed histologic features, MSH6 and other MMR immunohistochemistry, and accompanying MSI testing results (n=20). Heterogenous MSH6 loss was seen in colorectal carcinoma (n=18), endometrial carcinoma (n=3), and sebaceous neoplasm (n=1). In the 18 colorectal carcinoma cases, it accompanied complete loss of mutL homolog 1 (MLH1) or PMS2, or both. Heterogenous MSH6 loss was characterized by MSI and MSH6 C8 tract instability in treatment-naive cases and showed mucinous or signet-ring zones in one quarter of cases. Two cases status post neoadjuvant chemoradiation showed heterogenous MSH6 loss but were microsatellite and C8 tract stable. C8 tracts were unstable in 2 of 4 MSH6-associated Lynch syndrome (LS) tumors, but all 4 showed complete MSH6 loss on immunohistochemistry. Further, 12 such MSH6-associated LS cases showed complete MSH6 loss. In conclusion, heterogenous MSH6 loss is uncommon, usually caused by instability in MSH6 exon 5 polycytosine tract, and not associated with germline MSH6 mutation. Although heterogenous MSH6 loss provides evidence against germline MSH6 mutation, patients whose tumors exhibit this immunolabeling pattern may have LS due to a defect in a different MMR gene.

Germline MLH1 Mutations Are Frequently Identified in Lynch Syndrome Patients With Colorectal and Endometrial Carcinoma Demonstrating Isolated Loss of PMS2 Immunohistochemical Expression.

Current guidelines on germline mutation testing for patients suspected of having Lynch syndrome are not entirely clear in patients with tumors demonstrating isolated loss of PMS2 immunohistochemical expression. We analyzed the clinical and pathologic features of patients with tumors demonstrating isolated loss of PMS2 expression in an attempt to (1) determine the frequency of germline MLH1 and PMS2 mutations and (2) correlate mismatch-repair protein immunohistochemistry and tumor histology with germline mutation results. A total of 3213 consecutive colorectal carcinomas and 215 consecutive endometrial carcinomas were prospectively analyzed for DNA mismatch-repair protein expression by immunohistochemistry. In total, 32 tumors from 31 patients demonstrated isolated loss of PMS2 immunohistochemical expression, including 16 colorectal carcinomas and 16 endometrial carcinomas. Microsatellite instability (MSI) polymerase chain reaction was performed in 29 tumors from 28 patients with the following results: 28 tumors demonstrated high-level MSI, and 1 tumor demonstrated low-level MSI. Twenty of 31 (65%) patients in the study group had tumors demonstrating histopathology associated with high-level MSI. Seventeen patients underwent germline mutation analysis with the following results: 24% with MLH1 mutations, 35% with PMS2 mutations, 12% with PMS2 variants of undetermined significance, and 29% with no mutations in either MLH1 or PMS2. Three of the 4 patients with MLH1 germline mutations had a mutation that results in decreased stability and quantity of the MLH1 protein that compromises the MLH1-PMS2 protein complex, helping to explain the presence of immunogenic but functionally inactive MLH1 protein within the tumor. The high frequency of MLH1 germline mutations identified in our study has important implications for testing strategies in patients suspected of having Lynch syndrome and indicates that patients with tumors demonstrating isolated loss of PMS2 expression without a germline PMS2 mutation must have MLH1 mutation analysis performed.

Evolving approach and clinical significance of detecting DNA mismatch repair deficiency in colorectal carcinoma.

The last two decades have seen significant advancement in our understanding of colorectal tumors with DNA mismatch repair (MMR) deficiency. The ever-emerging revelations of new molecular and genetic alterations in various clinical conditions have necessitated constant refinement of disease terminology and classification. Thus, a case with the clinical condition of hereditary non-polyposis colorectal cancer as defined by the Amsterdam criteria may be one of Lynch syndrome characterized by a germline defect in one of the several MMR genes, one of the yet-to-be-defined "Lynch-like syndrome" if there is evidence of MMR deficiency in the tumor but no detectable germline MMR defect or tumor MLH1 promoter methylation, or "familial colorectal cancer type X" if there is no evidence of MMR deficiency. The detection of these conditions carries significant clinical implications. The detection tools and strategies are constantly evolving. The Bethesda guidelines symbolize a selective approach that uses clinical information and tumor histology as the basis to select high-risk individuals. Such a selective approach has subsequently been found to have limited sensitivity, and is thus gradually giving way to the alternative universal approach that tests all newly diagnosed colorectal cancers. Notably, the universal approach also has its own limitations; its cost-effectiveness in real practice, in particular, remains to be determined. Meanwhile, technological advances such as the next-generation sequencing are offering the promise of direct genetic testing for MMR deficiency at an affordable cost probably in the near future. This article reviews the up-to-date molecular definitions of the various conditions related to MMR deficiency, and discusses the tools and strategies that have been used in detecting these conditions. Special emphasis will be placed on the evolving nature and the clinical importance of the disease definitions and the detection strategies.

Role of endometrial cancer abnormal MMR protein in screening Lynch-syndrome families.

OBJECTIVE: To identify patients with endometrial cancer with potential Lynch-related DNA mismatch repair (MMR) protein expression defects and to explore the role of these defects in screening for LS. METHODS: Endometrial cancers from 173 patients recruited to the Nanchong Central Hospital were tested for MMR (MLH1, MSH2, PMS2, and MSH6) protein expression using immunohistochemistry (IHC). RESULTS: In the 173 tumor tissue samples, the expression loss rates of MSH6, MSH2, PMS2 and MLH1 protein were 16.18% (28/173), 12.14% (21/173), 7.51% (13/173) and 5.78% (10/173), respectively. The total loss rate of MMR protein was 29.89% (27/87). There were 19 patients with a family history of cancer, of which 18 patients demonstrated loss of expression of MMR protein. In the 22 abnormal MMR patients without family history, five families were found to have Lynch-associated cancer (colorectal cancer, endometrial cancer, ovarian cancer, stomach cancer) after follow-up for two years. CONCLUSION: MMR proteins play an important role in the progress of endometrial cancer. The routine testing of MMR proteins in endometrial cancer can contribute to the screening of LS families, especially small families.

Lynch syndrome screening should be considered for all patients with newly diagnosed endometrial cancer.

Lynch syndrome (LS) is an autosomal dominant inherited disorder caused by germline mutations in DNA mismatch repair (MMR) genes. Mutation carriers are at substantially increased risk of developing cancers of the colorectum and endometrium, among others. Given recent recommendations for universal, cost-effective screening of all patients with newly diagnosed colorectal cancer using MMR protein immunohistochemistry, we evaluated MMR protein expression in a series of endometrial cancers in the general population. A total of 605 consecutive cases of primary endometrial cancer at a single institution (1997 to 2013) were evaluated regardless of age, family history, or histologic features. Evaluation methods consisted of immunohistochemistry for the MMR proteins MLH1, MSH2, MSH6, and PMS2, followed by DNA methylation analysis for cases with MLH1/PMS2 deficiency. Germline mutation testing was performed on a subset of cases. Forty MMR-deficient, nonmethylated endometrial cancers were identified: 3 MLH1/PMS2 and 37 MSH6/MSH2 protein deficiencies. Only 25% occurred in women below 50 years of age (range, 39 to 88 y), 1 of which was in a risk-reducing hysterectomy specimen. Only 15% of patients had a prior history of carcinoma, including only 2 patients with prior colorectal carcinoma. Most (80%) of the endometrial cancers were purely endometrioid; there were 2 mixed endometrioid/mucinous, 1 mucinous, 1 serous, 2 clear cell, and 2 carcinosarcoma cases. When grading was applicable, 40% of the endometrial malignancies were FIGO grade 1, 34% grade 2, and 26% grade 3. Thirteen percent arose in the lower uterine segment, and 23% had tumor-infiltrating lymphocytes. Of the tumors with known germline testing, 41% with a LS-associated germline mutation were not associated with any of the traditional indicators that have been recommended for LS screening (ie, age 50 y or younger, personal/family cancer pedigree that meets Bethesda guideline criteria, presence of MMR-associated tumor morphology, or location in the lower uterine segment). These data suggest that a significant number of LS-associated endometrial carcinomas are missed using clinical, histologic, and locational screening parameters and provide support for universal screening of all newly diagnosed endometrial cancers.

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.

Risk of secondary malignancy (including breast) in patients with mismatch-repair protein deficiency.

Lynch syndrome (LS) is an autosomal dominant inherited disease that is associated with an increased risk for colorectal and endometrial cancer due to germline mutations in mismatch-repair (MMR) genes. Whereas primary tumors in this syndrome are widely recognized, the relative risk(s) of secondary malignancies, particularly breast cancer, in LS patients are still poorly characterized. To provide an improved assessment of these risks, MMR status was evaluated in secondary tumors from a series of patients with index tumors of known MMR status (both proficient and deficient). A total of 1252 tumors (index tumors) and all secondary malignancies were tested for MMR by immunohistochemistry (MSH2, MSH6, MLH1, PMS2) between 1992 and 2013. Tumors with MLH1/PMS2 deficiency were tested for hypermethylation or BRAF mutation, when appropriate. Of the 1252 index tumors, 162 were MMR deficient (dMMR), and, of that subset, 32 secondary tumors were identified (19.7%). In contrast, 80 secondary tumors were identified in the proficient (intact) group (7.3%). Although secondary malignancies were more common in the dMMR group (P=0.0001), there was no trend in tumor type. Specifically, breast cancer was not overly represented in the dMMR group. When secondary tumors had dMMR, they were more likely to have deficiency in MSH2/MSH6 than in MLH1/PMS2 (P=0.01). Of the patients with tumors exhibiting dMMR, women were more likely to have a dMMR secondary tumor in this series (P=0.0001); however, breast cancer was not overly represented, and our study provides no evidence that it is more frequent in LS. MSH2/MSH6 deficiency is more commonly associated with a secondary tumor compared with MLH1/PMS2 deficiency, when methylation/BRAF status is taken into account.

[Immunohistochemical examination of MSH2, PMS2, MLH1, MSH6 compared with the analysis of microsatellite instability in colon adenocarcinoma].

Adenocarcinoma of the colon in 10-20% is associated with microsatellite instability, which can occur both in sporadic cancers and in hereditary nonpolyposis colon cancer. Our analysis of 195 cases of adenocarcinoma of the colon showed that microsatellite instability (MSI-H) was found only in 1.5% of patients. Subsequent choice of patients with suspected hereditary Lynch syndrome led to the identification of additional 17 patients with microsatellite instability. They passed an analysis of genes of repair system of unpaired nucleotides of DNA. The study showed that immunohistochemical staining of MSH2, MSH6, MLH1, PMS2 could effectively conduct a preliminary screening of the Lynch syndrome but was unable to divide cases of sporadic and hereditary MSI-H colon cancer.

Pyloric gland adenoma in Lynch syndrome.

The prevalence of gastric cancer associated with Lynch syndrome (LS) is highly variable, and the underlying histologic pathway or molecular mechanisms remain unclear. From 1995 to 2012, 15 patients had been treated for both gastric and colonic adenocarcinomas and diagnosed as LS. In all cases, pathologic review, immunohistochemical analysis for mismatch-repair proteins, and microsatellite instability (MSI) tests were performed. To confirm LS, germline mutation tests and multiplex ligation-dependent probe amplification were performed. All gastric and colonic carcinomas were MSI-high and lost expressions of MLH1/PMS2 in 11 (73%) cases and MSH2/MSH6 in 4 (27%) cases. Remarkably, in a patient with LS and germline mutation of MLH1 gene, pyloric gland adenoma (PGA) transformed to adenocarcinoma during follow-up. In 2 additional cases, PGA was found adjacent to advanced gastric cancers. All PGAs in LS patients were MSI-high and lost expression of mismatch-repair proteins (MLH1/PMS2 in 2 cases and MSH2/MSH6 in 1 case), whereas none of the 14 sporadic PGAs was MSI-high or had lost expression of mismatch-repair proteins. On the basis of these observations, although very rare, we suggest the possibility that PGA may be a precursor lesion to gastric adenocarcinoma in LS and that the mismatch-repair deficient pathway of carcinogenesis is involved early in the gastric carcinogenesis pathway.

Association of tumor morphology with mismatch-repair protein status in older endometrial cancer patients: implications for universal versus selective screening strategies for Lynch syndrome.

Although there is consensus on the cost-effectiveness of a universal approach of screening all colorectal cancer patients for Lynch syndrome (LS) using mismatch-repair (MMR) protein immunohistochemistry (IHC) and/or microsatellite instability (MSI) testing, the question of universal versus selective screening of endometrial cancer patients remains to be resolved. We have prospectively implemented a selective screening algorithm for newly diagnosed endometrial cancer patients, triggered by patient age 50 years or younger, personal/family cancer pedigree that meets Bethesda guideline criteria, and/or presence of MMR-associated tumor morphology. Four-protein MMR IHC and MSI testing were performed if any of the criteria were met. This algorithm excluded screening of older patients without a cancer pedigree and whose tumors lacked MMR morphology. The aim of this study was to retrospectively determine whether these exclusion criteria missed any tumors with abnormal MMR. Among 273 consecutive patients with newly diagnosed endometrial cancers, 181 (66%) lacked criteria for screening. Retrospective MMR IHC confirmed intact MMR in 177 (97.8%) of these 181 unscreened patients, loss of MSH6 in 1 patient (0.5%), and loss of MSH1/PMS2 due to MLH1 promoter hypermethylation in 3 patients (1.7%). In comparison, 41% of patients fulfilling 1 or more criteria for screening had abnormal MMR IHC/MSI, mostly consisting of loss of MLH1/PMS2. MMR morphology contributed to detection of 92% of the abnormal MMR cases while cancer pedigree contributed to detection of the remainder. All of the abnormalities due to MSH2 and PMS2 were detected by the screening algorithm, but 1 of the 4 MSH6 cases was not. The latter finding is consistent with the literature that MSH6 endometrial cancers exhibit a phenotype different than those of the other MMR genes. We conclude that a genotype-specific approach to screening endometrial cancer for LS could consist of universal testing by MSH6 IHC and selective testing by MLH1, PMS2, and MSH2 IHC on the basis of age, cancer pedigree, and MMR morphology. Cost-effectiveness of this hybrid selective strategy deserves further study, particularly in comparison with a universal strategy. Further work to identify phenotypic features of endometrial cancers with methylated MLH1 that would allow them to be excluded from LS screening would also contribute to cost-effectiveness.

Managing young colorectal cancer: a UK and Irish perspective.

OBJECTIVE: Young patients with familial syndromes have an increased metachronous cancer rate. Effective management is possible by identifying this high-risk group prior to index colectomy. The study surveys the Association of Coloproctology of Great Britain and Ireland (ACPGBI) membership preoperative evaluation and clinical management in young patients with colorectal cancer (CRC). METHOD: An electronic survey was sent to the membership of the ACPGBI. The survey polled members on clinical scenarios relating to young-onset CRC patients. We were particularly concerned with preoperative management strategies, the extent of colectomy, and postoperative surveillance. Survey responses were collated and analysed. RESULTS: A total of 124 members responded to the survey and 74 completed the survey. Of these, 87.8 % would proceed to colectomy without preoperative tumor or genetic testing. Decisions regarding the extent of colectomy depended on family history. A total of 67 (90.6 %) would offer a limited colectomy with no family history, 49 (66.2 %) in a patient with familial CRC type X, 29 (39.2 %) in a young patient with Lynch syndrome. A similar trend was seen with young rectal cancer. Only 16 surgeons (21.6 %) could identify a syndrome of MYH-associated polyposis (MAP). CONCLUSION: The majority of ACPGBI members will not offer preoperative risk testing based on a young age alone; however, the majority would alter their surgical strategy based on the results of this testing. MAP is poorly recognized by ACPGBI members and therefore an opportunity exists for education among members. WHAT IS NEW IN THIS PAPER?: This study is the first paper to survey the ACPGBI membership on management practices in young-onset CRC. Members are poor in adopting preoperative testing, alter surgical strategy based on a familial syndrome, with a minority recognizing MAP. An opportunity to improve education on young CRC patients exists.

Epithelial-mesenchymal transition in colorectal cancer tissue of patients with Lynch syndrome.

AIM: To explore the epithelial-mesenchymal transition (EMT) in tissue from patients with Lynch syndrome, and to interpret biological behaviour of Lynch syndrome. METHODS: Sixty-eight formalin-fixed and paraffin embedded tissue blocks were analyzed in this study, including tissues from Lynch syndrome (n = 30), sporadic colorectal carcinoma (CRC) (n = 30), and tumor-adjacent tissues (n = 8). Tissue sections were stained for human mutS homolog 2 (hMSH2), human mutL homolog 1 (hMLH1), transforming growth factor-ß type II receptor (TGFßRII), E-cadherin, ß-catenin, matrix metalloproteinase-7 (MMP-7) and tissue inhibitor of metalloproteinase-2 (TIMP-2) by immunohistochemical staining. Furthermore, clinical data such as age, gender and tumor-node-metastasis stage were also collected retrospectively. RESULTS: The positive expression rates of hMSH2, hMLH1, TGFßRII, E-cadherin, ß-catenin, MMP-7 and TIMP-2 were significantly related to the depth of invasion and lymph node metastasis, but not to sex or tumour size or location. The differences in the positive expression rates of hMSH2, hMLH1, TGFßRII, E-cadherin, cytomembrane ß-catenin, cytoplasmic ß-catenin, MMP-7 and TIMP-2 were significant between sporadic CRC and Lynch syndrome. The expression of hMSH2 had a positive correlation with that of hMLH1 in Lynch syndrome and sporadic CRC. The expression of TGFßRII had a positive correlation with that of hMSH2, hMLH1 and MMP-7, and a negative correlation with that of TIMP-2. The expression of MMP-7 had a negative correlation with that of TIMP-2 in Lynch syndrome and sporadic CRC. The expression of E-cadherin was positively correlated with that of cytomembrane ß-catenin. However, the expression of cytomembrane ß-catenin was negatively correlated with that of cytoplasmic ß-catenin, and the expression of cytoplasmic ß-catenin was positively correlated with that of MMP-7. CONCLUSION: EMT may play an important role in the development and progression of Lynch syndrome. Lynch syndrome was caused by the mutations of mismatch repair genes, mainly hMSH2 and hMLH1, which also beget the mutational inactivation of TGFßRII. Therefore, the colorectal cancer of Lynch syndrome can escape the inhibitory effect of TGFß1. However, TGFß1 can up-regulate the expression of MMP-7 and down-regulate the expression of TIMP-2 in tumors by disassembling the E-cadherin/ß-catenin complex in the cytomembrane.

The molecular basis of EPCAM expression loss in Lynch syndrome-associated tumors.

Germline deletions affecting the epithelial cell adhesion molecule (EPCAM) gene lead to silencing of MSH2 and cause Lynch syndrome. We have recently reported that lack of EPCAM expression occurs in many, but not all tumors from Lynch syndrome patients with EPCAM germline deletions. The differences in EPCAM expression were not related to the localization of EPCAM germline deletions. We therefore hypothesized that the type of the second somatic hit, which leads to MSH2 inactivation during tumor development, determines EPCAM expression in the tumor cells. To test this hypothesis and to evaluate whether lack of EPCAM expression can already be detected in Lynch syndrome-associated adenomas, we analyzed four carcinomas and two adenomas from EPCAM germline deletion carriers for EPCAM protein expression and allelic deletion status of the EPCAM gene region by multiplex ligation-dependent probe amplification. In four out of six tumors we observed lack of EPCAM expression accompanied by biallelic deletions affecting the EPCAM gene. In contrast, monoallelic retention of the EPCAM gene was observed in the remaining two tumors with retained EPCAM protein expression. These results demonstrate that EPCAM expression in tumors from EPCAM deletion carriers depends on the localization of the second somatic hit that inactivates MSH2. Moreover, we report lack of EPCAM protein expression in a colorectal adenoma, suggesting that EPCAM immunohistochemistry may detect EPCAM germline deletions already at a precancerous stage.

Synchronous breast cancers with different morphologic and molecular phenotypes occurring in Lynch syndrome: what does the heterogeneity imply?

The increasingly widespread use of immunohistochemistry in the detection of DNA mismatch repair proteins has led to the observation of various unusual tumor types that occur in Lynch syndrome and exhibit mismatch repair protein deficiency. Understanding the clinical significance of such unusual tumors has become increasingly desirable. Here, we report a case of 2 synchronous breast cancers occurring in a 74-year-old woman who carried a deleterious germline mutation in MSH2 and who survived an endometrial and a colonic carcinoma. Both breast cancers were of lobular type with similar expression patterns for estrogen receptor, progesterone receptor, and Her2/neu. However, the 2 cancers differed in other characteristics. One tumor showed a solid alveolar histologic pattern with prominent tumor-infiltrating lymphocytes and loss of MSH2 and MSH6 protein on immunohistochemical staining. In contrast, the other tumor was of classic type with no apparent lymphocytic infiltration and no loss of mismatch repair protein. Such a case carries practical implications as it suggests that certain breast cancers may serve as tissue samples for the detection of mismatch repair deficiency in families at high risk for Lynch syndrome, thus expanding the test sample repertoire for genetic workup in these families. Furthermore, the case exemplifies the complexity of tumorigenesis in Lynch syndrome patients. The observation that, of the 2 breast cancers, increased tumor-infiltrating lymphocytes were present only in the tumor that showed mismatch repair protein abnormality is in keeping with what has been observed in the colon and other sites. Such persistent genotype-phenotype correlation across different organs affords the promise that molecular classification may allow identification of biologically distinct tumor subsets beyond the confines of the tumor's primary anatomic location.