Loss Of PMS2 Research Articles

364P Prevalence, treatment and survival of NTRK gene fusions in microsatellite instable metastatic colorectal cancer patients

TRK inhibitors are a treatment option for patients with NTRK fusions positive tumors, including metastatic colorectal cancer (mCRC). However, the clinical behavior, including response to standard therapy and overall survival, in NTRK fusion positive mCRC is unknown which complicates the interpretation of tumor agnostic basket trials studying TRK inhibitors. We aim to estimate the prevalence of NTRK fusions in microsatellite instable (MSI) mCRC and to determine patient characteristics and clinical behavior of this NTRK fusion subtype. FFPE tissue was requested from all MSI mCRC patients diagnosed between 2015 and 2020 in the Netherlands. Pan-Trk immunohistochemistry was used as screening method. Positive cases were analyzed by RNA-based NGS with Archer or FFPE-targeted locus capture to assess NTRK1, 2, and 3 rearrangements. Clinical data were retrieved from the Netherlands Cancer Registry. In total, 8 out of 203 tumors (3,9%) harbored an NTRK fusion: 7 rearrangements were found in the NTRK1 gene and 1 NTRK3-ETV6 fusion was detected. All NTRK-fusion positive tumors were RAS and BRAF wild-type. In the subgroup (n = 26) of RAS and BRAF wild-type MSI patients, prevalence of NTRK fusions was 23%. All NTRK-fusion positive tumors showed loss of MLH1 and PMS2 and MLH1 promotor hypermethylation was found in 7 out of 8 tumors. Benefit from chemotherapy (1/6) or anti-EGFR therapy (0/2) in NTRK-fusion positive patients was limited, but all four immunotherapy-treated patients had ongoing responses and a minimum overall survival of 470 days. The four patients who did not receive immunotherapy had a short overall survival (range 11-282 days). In this population wide cohort study, NTRK fusions are most prevalent (23%) in RAS and BRAF wild-type MSI mCRC patients. This is the first study to suggest resistance to chemotherapy and anti-EGFR therapy in NTRK-fusion positive tumors leading to impaired overall survival. In contrast, immunotherapy seems to be effective in NTRK-fusion positive patients. The clinical condition of the patient probably dictates the choice of upfront immunotherapy versus TRK inhibitors in this subgroup. We recommend early testing for NTRK fusions in RAS and BRAF wild-type MSI patients.

To Test or Re-Test, that is the Question: Comparison of the Mismatch Repair Deficiency between Primary and Recurrent Sites of Uterine Cancers (088)

To Test or Re-Test, that is the Question: Comparison of the Mismatch Repair Deficiency between Primary and Recurrent Sites of Uterine Cancers (088)

DAXX, ATRX, and MSI in PanNET and Their Metastases: Correlation with Histopathological Data and Prognosis

Introduction: Studies on pancreatic neuroendocrine tumors (PanNETs) regarding loss of ATRX, DAXX, or frequency of microsatellite instability (MSI) show inconclusive results. So far, data on corresponding metastaseshave not been published. Methods: We performed immunohistochemistry (IHC) of ATRX, DAXX, MSH2, MSH6, MLH1, and PMS2 on 74 PanNETs and 19 metastases. ATRX- and DAXX-negative PanNETs were further sequenced for mutations. We used polymerase chain reaction for MSI on cases with IHC loss of MSH2, MSH6, MLH1, and PMS2. Results: Immunohistochemical loss of DAXX and ATRX was observed in 8/74 (11%) and 6/74 (8%) PanNETs. Loss of DAXX immunoreactivity was statistically associated with higher tumor grade and showed a tendency toward a decreased overall survival. Sequencing of DAXX- (7/11 [64%]) and ATRX-negative (5/11 [45%]) PanNETs revealed a mutation in 6/7 (86%) and 2/5 (40%). The specificity of immunohistochemical loss of DAXX and ATRX for mutation was 80% and 67%, respectively. The expression status of DAXX compared to primary tumor differs in 2/12 (17%) lymph node metastases. We further identified 3/74 (4%) tumors as MSI, associated with a poor prognosis. Discussion/Conclusion: Our study supports the hypothesis that a loss of DAXX immunoreactivity can identify a more aggressive subtype of PanNET with high confidence, while ATRX loss is a weaker indicator. Our results also strengthen the role of DAXX immunolabeling as a prognostic marker. We could show that ATRX might be less suitable as a surrogate for sequencing. Our results indicate that IHC of DAXX and ATRX may identify PanNET subtypes as targets for more aggressive therapy.

P-268 Molecular signature and MMR status of early- and late-onset colorectal cancer among Arabs

Early-onset colorectal cancer (EO-CRC) is increasing in alarming pace globally. Ethnical/ racial disparities in the EOCRC clinicopathological and molecular signatures have been reported from different geographical regions. There is scarce data about the status and molecular features of the disease among Arabs despite the noticable increasing incidence. The aim of this study is to describe the clinicopathological parameters, molecular signatures and MMR status of early and late onset CRC among Arab patients. Then we compare these findings with finding from other ethnic groups reported from other geographical regions. This is a retrospective cohort study that included patients with pathologically confirmed colorectal cancer treated between 2015-2021 in Sultan Qaboos University Hospital, Oman. Data were collected from electronic health records. Clinicopathological data along with MMR status, KRAS and BRAF data were collected. EOCRC was defined as CRC at = 50years old. Clinicopathological and molecular features were compared between EOCRC and LOCRC and then compared with published data from other ethnic groups. Of 254 patients diagnosed with CRC, 80 (31.5 %) had EOCRC. Gender, stage, and tumor sidedness were similar between the EOCRC and LOCRC groups. Male gender was dominant (55%) among both groups. Adenocarcinoma was the most common type among EOCRC (58, 72.5%) and LOCRC (127, 73%) followed by signet (8.7% and 1.1%) which was significantly different (p = 0.01). Forty of EOCRC patients (50%) presented with advanced metastatic stage compared to 76 (43.6%) of LOCRC (P = .038). There is no difference in tumor sidedness in both groups where majority (77% of EOCRC, 76% of LOCRC) of patients presented with left sided tumor (P = 0.1). Rectum was involved in 38 (46.5%) of EOCRC and 74 (42.5%) of LOCRC. All 4 MMR proteins were expressed in 57 (71%) of EOCRC and 107 (61%) of LOCRC cases, where they were classified as MMR proficient (pMMR). Nine patients from the LOCRC group and five from the EOCRC group had one or more abnormal MMR proteins and were classified as MMR deficient (dMMR). Three of them are suspicious of having Lynch syndrome since they have a wild-type BRAF as well. The remaining had loss of both MLH1 and PMS2. KRAS status was checked for 105 patients (64 LOCRC and 41 EOCRC). Thirty-eight (21.8%) of LOCRC and 16 (20%) of EOCRC are wild KRAS type. Compared with reported findings from other geographhical regions, this data did not show a significant differnece between EOCRC and LOCRC at the clinicopathological and molecular level. EOCRC and LOCRC among Arabs are almost similar in term of clinicopathological and molecular signatures. Studies from other geographical regions reported distinct features that differentiate the two entities which was not obvious in this study. More studies are needed to correlate these clinicopathological and molecular signatures with patients' outcome and type of management received. Subsequently, specific molecular studies tailored to different racial/ethnic group would be the way to understand and tackle this alarming increase in EOCRC incidence.

Prevalence of mismatch repair mutations in colorectal carcinoma patients in Mangalore

Colorectal cancer (CRC) is highly prevalent throughout the world and represents the 3rd most common cancer in men and the 2nd in women worldwide. Microsatellite instability (MSI) is a term used to denote a hypermutable phenotype caused by the loss of DNA mismatch repair (MMR) activity, and is a phenomenon now linked to the pathways of colorectal carcinogenesis. Compounding its importance is its integral association with Lynch syndrome, the most common cause for CRCs in young individuals. In the present study, we aimed to analyse the proportion of patients with risk of microsatellite instability by checking for loss of immunostaining for mismatch repair (MMR) proteins.From January 2016 to December 2016 and May 2017 to October 2017, 40 consecutive newly diagnosed cases of colorectal cancer were included in the study. The expression of MMR proteins in the tumour tissue using IHC for MSH2, MSH6, MLH1 and PMS2 was studied.Among the 40 cases, 3 (7.5%) demonstrated loss of MMR proteins and 37 (92.5%) cases had intact nuclear expression. Out of the three cases with MMR loss, one showed concurrent loss of MLH1 and PMS2, the second showed concurrent loss of MSH2 and MSH6 and the third showed an isolated loss of MSH6.Colorectal carcinomas showing MMR mutations are seen in the Mangalorean population. However, the incidence in our study was relatively low compared to most other studies, probably due to a variation in ethnicity.

Endometrial neuroendocrine carcinoma and undifferentiated carcinoma are distinct entities with overlap in neuroendocrine marker expression.

Dedifferentiated endometrial carcinomas (DDECs)/undifferentiated endometrial carcinomas (UDECs) frequently harbour genomic activation of switch/sucrose non-fermentable (SWI/SNF)-complex proteins, and can show histological overlap with neuroendocrine carcinoma (NEC). The aim of this study was to compare the extent of the expression of neuroendocrine markers, SWI/SNF proteins and mismatch repair (MMR) proteins in DDEC/UDEC and NEC. The extent of expression of synaptophysin, chromogranin, CD56, ARID1A, ARID1B, SMARCA4, SMARCB1 and MMR proteins was evaluated by immunohistochemistry on 44 SWI/SNF-deficient DDECs/UDECs and 15 NECs. Thirty-three of 44 (75%) DDECs/UDECs showed expression of at least one neuroendocrine marker, with 18 of 44 (41%) expressing two or more neuroendocrine markers, whereas all 15 NECs showed expression of at least one neuroendocrine marker, with 14 of 15 (93%) expressing two or more neuroendocrine markers. Neuroendocrine marker expression in DDECs/UDECs was typically focal when present, with average extents of 17%, 4% and 8% for synaptophysin, chromogranin and CD56 in the positive cases, respectively, in contrast to 73%, 40% and 62% in the positive NEC cases, respectively. All 15 NECs showed intact expression of SWI/SNF-complex proteins, except for one that showed isolated loss of ARID1A. Thirty-eight of 44 DDECs/UDECs were MMR-abnormal (34 with loss of MLH1 and PMS2, and four with loss of PMS2 alone), whereas all NECs retained MMR protein expression. Our study demonstrates frequent but typically focal neuroendocrine marker expression in SWI/SNF-deficient DDECs/UDECs, whereas NECs typically express two or more neuroendocrine markers, with diffuse expression of at least one marker. ARID1B, SMARCA4 and SMARCB1 immunohistochemistry can be used to aid in the differentiation between DDEC/UDEC and NEC.

Percent Agreement Between Immunohistochemistry and Next-Generation Sequencing in Testing Patients for Mismatch Repair Deficiency.

The presence of mismatch repair deficiency is frequently assessed in gastrointestinal and gynecologic neoplasms by surgical pathologists using immunohistochemical methods. Targeted next-generation sequencing (NGS) covering some genes in the mismatch repair complex is used with increasing frequency, however, the percent positive and negative agreement of immunohistochemical methods and NGS of mismatch repair genes is not well-described in the literature. We sought to compare performance of immunohistochemistry (IHC) and NGS of mismatch repair genes on our institutional targeted panel. We evaluated the concordance of immunohistochemical and panel-based gene sequencing methods in a retrospective cohort study of patients evaluated at our center with both immunohistochemical and panel-based sequencing. Our NGS panel covers only MLH1 and MSH2, whereas our immunohistochemical panel assesses for expression of MLH1, PMS2, MSH2, and MSH6. We identified 68 unique patients with both immunohistochemical evaluation of mismatch repair protein expression and NGS panel sequencing, of which 67 were suitable for analysis given the patterns of immunohistochemical loss of expression observed. The percent positive agreement for NGS with IHC was 50%, albeit with very rare positive cases (n=2/4). Percent negative agreement was also high at 100% (n=63/63). One case with loss of MLH1, PMS2, and MSH6 expression by IHC and no pathogenic variants by NGS exhibited MLH1 promoter hypermethylation. Percent negative agreement between immunohistochemical and NGS gene sequencing is high, although firm conclusions regarding percent positive agreement between NGS and IHC are limited by low numbers of positive cases in our cohort. In general, we consider the findings to support continued use of immunohistochemical methods to screen for the presence of mismatch repair deficiency and consider additional testing by NGS likely to add little diagnostic value in the context of intact immunohistochemical expression of mismatch repair proteins.

An unusual phenotype occurs in 15% of mismatch repair-deficient tumors and is associated with non-colorectal cancers and genetic syndromes

Immunohistochemistry (IHC) and/or MSI-PCR (microsatellite instability-polymerase chain reaction) tests are performed routinely to detect mismatch repair deficiency (MMR-D). Classical MMR-D tumors present a loss of MLH1/PMS2 or MSH2/MSH6 with MSI-High. Other profiles of MMR-D tumors have been described but have been rarely studied. In this study, we established a classification of unusual MMR-D tumors and determined their frequency and clinical impact. All MMR-D tumors identified between 2007 and 2017 were selected. Any profile besides the classical MMR-D phenotype was defined as unusual. For patients with unusual MMR-D tumors, IHC, and PCR data were reviewed, the tumor mutation burden (TMB) was evaluated and clinical and genetic features were collected. Of the 4948 cases of MMR testing, 3800 had both the available IHC and MSI-PCR results and 585 of these had MMR-D. After reviewing the IHC and PCR, 21% of the cases initially identified as unusual MMR-D were reclassified, which resulted in a final identification of 89 unusual MMR-D tumors (15%). Unusual MMR-D tumors were more often associated with non-CRC than classical MMR-D tumors. Unusual MMR-D tumors were classified into four sub-groups: i) isolated loss of PMS2 or MSH6, ii) classical loss of MLH1/PMS2 or MSH2/MSH6 without MSI, iii) four MMR proteins retained with MSI and, iv) complex loss of MMR proteins, with clinical characteristics for each sub-group. TMB-high or -intermediate was shown in 96% of the cancers studied (24/25), which confirmed MMR deficiency. Genetic syndromes were identified in 44.9% (40/89) and 21.4% (106/496) of patients with unusual and classical MMR-D tumors, respectively (P < 0.001). Five patients treated with an immune checkpoint inhibitor (ICI) had a prolonged clinical benefit. Our classification of unusual MMR-D phenotype helps to identify MMR deficiency. Unusual MMR-D phenotype occurs in 15% of MMR-D tumors. A high frequency of genetic syndromes was noted in these patients who could benefit from ICI.

Two-Antibody Staining Method, A Cost-Saving Strategy for Universal Lynch Syndrome Screening in Endometrial Cancers

Objective: Lynch syndrome is an autosomal dominant disorder that increases the risk of cancers in many sites. In women, endometrial cancer is often a sentinel tumor and thus immunohistochemistry for mismatch repair (MMR) proteins MLH1, MSH2, MSH6 and PMS2 is encouraged as a screening test. To reduce cost, staining for only 2 MMR proteins PMS2 and MSH6 has been proposed. This study aimed to determine whether a 2-antibody staining test is enough to screen for Lynch syndrome in endometrial cancer patients.Materials and Methods: Cases of endometrial carcinoma with immunohistochemistry for 4 MMR proteins were reviewed. Results of immunohistochemistry screening were compared between all four antibodies and only two (PMS2 and MSH6) antibodies.Results: Loss of expression of any MMR proteins was detected in 51 out of 203 cases (25.12%). Twenty-three cases (45%) showed loss of MLH1 and PMS2; 13 cases (25%) showed loss of MSH2 and MSH6; five cases (10%) showed loss of MSH6; seven cases (14%) showed loss of PMS2 and three cases (6%) showed loss of MSH2. The 2-antibody method detected 48 cases (94%) with a MMR deficiency but failed to detect three cases (6%) with an isolate loss of MSH2. The screening results from the 2-antibody method are 98.5% (200/203) in accordance with the original 4-antibody method.Conclusion: The 2-antibody method is a quite effective option to screen for Lynch syndrome in endometrial cancers. However, MSH2 mutations may be missed in a few cases.

Clinical outcomes of neoadjuvant treatment strategies in localized mismatch repair-deficient rectal cancer.

192 Background: Rectal cancer treatment paradigm has been evolving over time. Historically, for locally advanced rectal cancer, standard therapy (ST) consisted of neoadjuvant chemoradiation followed by surgery and adjuvant chemotherapy. Recently, total neoadjuvant treatment (TNT) approach that delivers both neoadjuvant chemotherapy (CAPOX or FOLFOX) and chemoradiation (or radiation only) prior to surgery is increasingly being utilized. The prognostic and predictive values of mismatch repair deficient (dMMR) in rectal cancer is not well characterized. Most dMMR patients receive the same treatment as MMR proficient (pMMR) patients although there is limited data that dMMR rectal cancer patients may not have the same level of benefits from neoadjuvant treatment. This retrospective study aims to evaluate the clinicopathological/molecular characteristics, disease response, and clinical outcomes in dMMR localized rectal cancer patients. Methods: A retrospective analysis was conducted on consecutive adult patients with a diagnosis of dMMR rectal cancer who were treated at Mayo Clinic between January 2000 to September 2021. Patients who presented with concurrent primary non-colorectal malignancies were excluded. The distributions of demographics, clinicopathological features, biomarkers, and outcome data were collected. Survival was assessed using Kaplan-Meier curves and Cox models were stratified by treatment arms to determine significance of treatment strategies. Results: Forty-one patients were identified with a median age of 45.3 years. Thirty (73.2%) pts were male. The most common MMR were loss of MSH2 and MSH6 (12/42; 29.3%) followed by loss of MLH1 and PMS2 (10/42; 24.4%) and solitary loss of MSH2 (4/42; 9.8%). The treatment, pathological response, and clinical outcomes are listed in table. With a median follow up of 101 months, only 6 patients (14.3%) died and median overall survival was not reached. Conclusions: Our findings showed dMMR localized rectal cancer responded to both ST and TNT with good clinical outcomes.[Table: see text]

Tumor board presentation of a woman with metastatic, hormone receptor‐positive, mismatch repair‐deficient endometrial cancer

Tumor board presentation of a woman with metastatic, hormone receptor‐positive, mismatch repair‐deficient endometrial cancer

Molecular Classification of Gastric Cancer With Emphasis on PDL-1 Expression: The First Report From Iran.

Background:Gastric cancer is one of the lethal cancers and there is no effective treatment for these patients and still, 5-year survival rate is about 25% to 30%. Finding reliable biomarkers for early-stage diagnosis, targeted therapy, and survival prediction is a priority in this cancer.Objectives:In this study we were trying to know about the molecular classification of gastric cancers in a group of patients from the South of Iran.Patients and Methods:In a cross sectional study, 50 specimens of gastric cancer were selected that have enough tissue to be stained by immunohistochemistry (IHC). IHC was performed for Her-2, mismatch repair genes (MLH-1, MSH-2, MSH-6, and PMS-2), and PDL-1. Frequency of positive makers was compared with survival and outcome.Results and Conclusion:In our study, deficient MMR (dMMR) was detected in 4 patients (8.0%). PD-L1 expression in tumor cells (TC) was observed in 1 of 4 cases (25%) with PMS2 loss. However, PD-L1 in TCs and TILs (tumor infiltrating lymphocytes) was negative in 1 case with MLH1 loss and in 3 of 4 cases with PMS2 loss, which was not statistically significant. All of our 50 cases were positive for MSH2 and MSH6, 24% of which showed TCs with PDL-1 expression and 32% of them in TIL. HER2 was positive in 2 (2/50, 4.0%) cases, among which all of the cases were positive for PD-L1 expression in TCs and TILs, respectively. However, in HER2-negative group, 26.2% (11/42) and 28.6% (12/42) of tumors were positive for PD-L1 in TCs and TILs, respectively. The expression rate of PD-L1 in HER2 negative TCs was significantly higher than that in HER2 positive TCs (P = .033). Immunohistochemistry for Her-2 was equivocal in 6 cases (12.0%) none of which expressed PD-L1 in tumor cells. In our study minimum and maximum survival times from detection of gastric cancer were 1 and 87 months, respectively. The mean ± SD and median ± SD of overall survival time were 30.69 ± 4.88 and 18 ± 1.45 months, respectively. One and 3-year survival rates of 40% and 24%, respectively. PD-L1 expression was not associated with survival, but its expression was associated with intestinal type Lauren classification and negative HER-2. PD-L1 positivity in tumor cells or tumor infiltrating lymphocytes was not an independent prognostic factor in gastric cancer.

Mismatch-Repair Deficiency in Follicular Lymphoma Tumors Is Common and Associated with a Favorable Overall Survival

Introduction: DNA mismatch repair (MMR) is a major mechanism cells use to repair erroneous insertion or deletion of bases during DNA replication. MMR deficiency (MMR-d), including rare germline mutations (Lynch syndrome) and somatic inactivation, has been extensively studied in solid tumors, such as colon, endometrial, pancreatic, and ovarian cancers. The prevalence of MMR-d in solid tumors ranges from 1% - 20% of somatic defects, and patients with MMR-d tumors have a longer overall survival. It is also well-known that MMR is an integral part of activation-induced cytidine deaminase (AID)-mediated somatic hypermutation and immunoglobulin class switch processes in normal mature B lymphocytes, while mice deficient in the MMR genes are prone to develop T and B cell lymphomas. It is also known that follicular lymphoma (FL) carries a high degree of somatic hypermutation with some heterogeneity induced by AID. Our understanding of MMR status in human blood cancers, especially in FL remains very limited. One could hypothesize that MMR-d status could permit cells to acquire and sustain high-degree of mutation rates, better sensitivity to DNA damaging chemotherapy while hindering rapid cell proliferation, which could manifest to a better prognosis in patients. Herein, we conducted an exploratory analysis to understand the frequency of MMR-d status and its prognostic significance in FL.Methods: Following approval of the Institution Review Board, we assessed the expression of MMR proteins; MLH1, PMS2 and MSH6 on formalin fixed paraffin embedded (FFPE) lymph node tissue obtained from patients with FL by immunohistochemistry (IHC) using standard methods on Ventana Benchmark XT automated stainers (Ventana Medical Systems, Tucson, AZ). Dako (clone ES05), Cell Marque (clone EPR3947) and Biocare (clone BC/44) antibodies were used to stain MLH1, PMS2 and MSH6, respectively. Fifty cases of FL with existing FFPE blocks were selected randomly. The expression of MLH1, PMS2 and MSH6 proteins in the tumor cells was scored as 0, +1 or +2, (Figure 1A). Cases with absence of the IHC signal (score of 0) in any one of the three proteins were classified as MMR-d. Progression free survival at 12 months (PFS12) or 24 months (PFS24) was defined as being free from disease progression or death at 12 or 24 months, respectively. All time-to-event analyses were done from the time of diagnosis.Results: Fifty patients with FL were included in the study. The median age at diagnosis was 65 years (range 34-85) and 58% were females. At initial diagnosis, 36 (72%) patients had advanced stage (stage 3, n=8, stage 4, n=28) disease. Of the 50 patients, 26 (52%) required treatment; chemotherapy (n=14), radiation treatment alone (n=9), surgery alone (n=3).Out of the 50 patients, 23 (46%) were classified as MMR-d due to lack of expression of one of the three assessed proteins: MLH1 (n=1, 2%), PMS2 (n=11, 22%) and MSH6 (n=19, 38%). The patient who had MLH1 loss had concomitant PMS2 loss. Stage IV disease was observed in 52% of the MMR-d patients and 59% in the MMR proficient (MMR-p) patients, p=0.77. Median age at diagnosis was 62 (range: 34-84) years and 67 (range: 34-85) years in MMR-d and MMR-p patients, respectively, p=0.1. FLIPI score was similar between the MMR-d [low n=10 (43%), intermediate n=9 (39%), high n=4 (18%)] and MMR-p [low n=5 (18%), intermediate n=14 (52%), high n=8 (30%)] patients, p=0.16. Fourteen (61%) of MMR-d patients required initiation of therapy upon diagnosis compared to 12 (44%) of MMR-p patients, p=0.27.The median follow-up for the entire cohort was 17 years [95% confidence interval (CI): 11.7-29.4]. The median overall survival (OS) of MMR-d patients was 10 years (95%CI: 7.8-20.7) compared to 6 years (95%CI: 4.5-NR) in MMR-p patients, p=0.036, Figure 1B. In patients with MMR-d and MMR-p, 83% and 55% achieved PFS12, p=0.04 and 65% and 41% achieved PFS24, p=0.08, respectively. After adjusting for FLIPI score, MMR status remained associated with OS (MMR-d HR: 0.51, 95%CI: 0.2-1.02, p=0.05).Discussion and Conclusion: In this pilot study, MMR-d in the FL tumors was common (46%) and, as predicted, was associated with a favorable OS. Association of MMR-d status with PFS in general and patients with early progression (short PFS12 and PFS24) and relationship of MMR-d with types of therapy need further study in large FL datasets. [Display omitted] DisclosuresPaludo: Karyopharm: Research Funding. King: Celgene/BMS: Research Funding. Maurer: Celgene: Research Funding; Genentech: Research Funding; Kite Pharma: Membership on an entity's Board of Directors or advisory committees; Morphosys: Membership on an entity's Board of Directors or advisory committees, Research Funding; Nanostring: Research Funding; Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees. Nowakowski: Celgene, NanoString Technologies, MorphoSys: Research Funding; Celgene, MorphoSys, Genentech, Selvita, Debiopharm Group, Kite/Gilead: Consultancy, Membership on an entity's Board of Directors or advisory committees. Witzig: Karyopharm Therapeutics, Celgene/BMS, Incyte, Epizyme: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celgene/BMS, Acerta Pharma, Kura Oncology, Acrotech Biopharma, Karyopharm Therapeutics: Research Funding.

Microsatellite unstable esophageal adenocarcinoma masquerading as a conventional esophageal primary

Abstract Introduction/Objective Patients with microsatellite instability (MSI) are susceptible to developing epithelial malignancies in multiple organs and systems, especially along the gastrointestinal tract. It’s important to know that MSI-tumors may present with an intriguing non-classical, “non-MSI-appearing”, histomorphology that deviates from the well-known MSI or Lynch syndrome spectrum. Pathologists should thus be prepared for unusual histopathological presentations in order to detect MSI and related therapeutic and prognostic targets. Ultimately, a timely and accurate classification is a crucial step in guiding clinical course. Methods/Case Report An 80-year-old male presented to an outside facility due to worsening dysphagia. Imaging and endoscopy studies confirmed a near-obstructing distal esophageal mass. Subsequently, an esophagogastrostomy was performed, which removed a moderately differentiated adenocarcinoma (pT3N1). The patient was managed with conventional chemotherapy after the surgery; however, due to progressive metastasis involving the liver, he was referred to our cancer center. Results (if a Case Study enter NA) Upon review of outside pathology materials, the tumor displayed irregularly arranged bizarre glands with eosinophilic cytoplasm and unusually large nuclei within the abundant fibrotic stroma. No intra-tumoral lymphocytes or “Crohn’s-like” pushing borders were identified. However, ancillary tests performed on acquired outside material showed loss of MLH1 and PMS2 with retained MSH2 and MSH6 in the tumor. Subsequent mutational analysis revealed additional MSI-related carcinogenic mutations. Accordingly, the previous regimen was switched to immunotherapy-based management. The patient remains disease-free 10-months later. Conclusion This unusual MSI esophageal adenocarcinoma exemplifies that such tumors may present with non- MSI/non-lynch histomorphology and that ancillary analyses should be carried out without reservation to evaluate microsatellite status. Thus, optimizing patient management and outcome.

Endometrial Adenocarcinoma Biopsies: Can Targeted Education Increase Reproducibility and Is It a Good Idea?

Abstract Introduction/Objective Assessing p53 mutation on biopsies could provide prognostic and therapeutic planning information, as it predicts worse outcomes for patients with endometrioid adenocarcinoma (EA). Immunohistochemistry (IHC) mutation pattern staining varies, easily causing misinterpretation. This study was designed to see if education clarifying staining issues would increase reproducibility, and if mutations detected in this setting were of prognostic import. Methods/Case Report p53 IHC on 46 FIGO grade 1 EA biopsies was scored by blinded participants. Education was provided regarding internal controls (IC), and common misinterpretations. The participants rescored to assess reproducibility. Outcome parameters (clinical stage [CS], progression free survival, higher FIGO grade on resection, and presence of mismatch repair mutations) were also assessed. Results (if a Case Study enter NA) 25% of scores changed post-education. Intraclass correlation among raters was 0.29 pre and 0.43 post (from fair to moderate). Mutation status changed in 5 cases. 2/5 caught IC failure for 1 case. Post-participation surveys found 0 participants were previously familiar with “high wild type,” and 60% were unfamiliar with cytoplasmic staining pattern, the possibility for heterogeneity, and necessary ICs. Every participant agreed grading was easier following education. Out of 6 patients with high CS disease (IIIC-IV), none had p53 mutation. 2/11 cases with higher FIGO grade (2-3) on resection had mutation. One patient had recurrence with no detectable mutation. 15/46 patients had MMR results available. No p53 mutation was detected in those with a loss of MLH1 and PMS2 (n=8). Conclusion Education on IHC issues can increase reproducibility in scoring, though overall reproducibility on biopsies was still subpar. Mutation detected in this setting did not correlate with current outcome parameters. Given the possibility of heterogenous expression and difficulties interpreting edge effect and assessing ICs in scant specimens, p53 IHC on EA biopsies is not recommended.

Investigation of discrepant mismatch repair immunohistochemistry and microsatellite instability polymerase chain reaction test results for gynecologic cancers using next-generation sequencing

Gynecologic cancers are routinely screened for DNA mismatch repair (MMR) gene mutations using immunohistochemistry (IHC) and/or polymerase chain reaction (PCR) for microsatellite instability (MSI) to enable selection of immune checkpoint inhibitor therapy and screen for Lynch syndrome. The limited data that compareIHC and MSI in endometrial tumors have shown discordance rates of 5-10%. We reviewed MMR/MSI results in gynecologic cancers and used next-generation sequencing (NGS) to interrogate discrepancies. Of the 328 cases with both IHC and MSI results, 256 (78.0%) were microsatellite stable (MSS) with preserved MMR (pMMR), 64 (19.5%) cases were MSI-High (MSI-H) with MMR deficient (dMMR), 2 cases showed subclonal loss of MLH1 and PMS2 with MSI-H, and 6 cases were discordant. Overall, there was a 98.2% (322/328) IHC/MSI concordance. Discordant cases were retested and/or subject to NGS. Of the six discrepant cases, five showed dMMR with MSS and one showed pMMR with MSI-H. One dMMR/MSI-L case showed loss of PMS2 with a germline pathogenic mutation. The pMMR/MSI-H case was found to harbor pathogenic variants in MLH1 and MSH6. One of the two cases with subclonal populations demonstrated MSI-H in the dMMR area and MSS in the pMMR area. These results emphasize the importance of selecting the appropriate tumor tissue for both IHC and molecular testing and demonstrate that NGS can help resolve discrepant MMR and MSI results.

Real-world outcome of universal screening for Lynch syndrome in Japanese patients with colorectal cancer highlights the importance of targeting patients with young-onset disease.

Despite the recommendations of the latest guidelines, the practical efficacy of universal screening for identifying Lynch syndrome (LS) among patients with colorectal cancer (CRC) may be limited in the real world due to infrequent referrals and the difficulties of genetic testing. Thus, the present study aimed to retrospectively analyze the results of universal screening of patients with CRC at a referral hospital in Japan. Immunohistochemistry was performed for mismatch repair proteins [including DNA mismatch repair protein MSH6 (MSH6), mismatch repair endonuclease PMS2 (PMS2), DNA mismatch repair protein Msh2 (MSH2) and DNA mismatch repair protein Mlh1 (MLH1)] and BRAF V600E mutation. Tumors that showed the following were considered to indicate LS and patients with such tumors were designated as genetic testing candidates (GTCs): i) Loss of MSH6/MSH2; ii) loss of MSH6 alone; iii) loss of PMS2 alone; and iv) loss of PMS2/MLH1 with negative BRAF V600E. MLH1 methylation and BRAF V600E mutation were analyzed in deficient mismatch repair (dMMR) tumors retrospectively. The frequency of dMMR and GTCs in an independent cohort of patients with young-onset CRC were also investigated. Universal screening revealed dMMR tumors, GTCs and LS probands in 7.3, 3.9 and 0.4%, respectively, of 463 patients with CRC. Although dMMR tumors were observed in both younger (<50 years) and older (≥60 years) patients, the GTCs were enriched in younger individuals. Evaluation of mismatch repair status in an independent cohort confirmed the high rate of GTCs in patients with young-onset CRC. The low detection rate of LS demonstrated in this study questions the implementation of routine universal screening in regions with low prevalence of LS. Considering the enrichment of GTCs in young-onset CRCs, age-restricted strategies may be simple and efficient practical alternatives to universal screening in the real world.

Distinct mutational profile and immune microenvironment in microsatellite-unstable and POLE-mutated tumors

IntroductionMismatch repair (MMR)-deficient and DNA polymerase epsilon (POLE)-mutated tumors exhibit a high tumor mutation burden (TMB) and have been proven to be associated with good responses to immune checkpoint inhibitor...

Genomic comparison between cerebrospinal fluid and primary tumor revealed the genetic events associated with brain metastasis in lung adenocarcinoma

Lung adenocarcinoma (LUAD) is most common pathological type of lung cancer. LUAD with brain metastases (BMs) usually have poor prognosis. To identify the potential genetic factors associated with BM, a genomic comparison for BM cerebrospinal fluid (CSF) and primary lung tumor samples obtained from 1082 early- and late-stage LUAD patients was performed. We found that single nucleotide variation (SNV) of EGFR was highly enriched in CSF (87% of samples). Compared with the other primary lung tissues, copy number gain of EGFR (27%), CDK4 (11%), PMS2 (11%), MET (10%), IL7R (8%), RICTOR (7%), FLT4 (5%), and FGFR4 (4%), and copy number loss of CDKN2A (28%) and CDKN2B (18%) were remarkably more frequent in CSF samples. CSF had significantly lower tumor mutation burden (TMB) level but more abundant copy number variant. It was also found that the relationships among co-occurrent and mutually exclusive genes were dynamically changing with LUAD development. Additionally, CSF (97% of samples) harbored more abundant targeted drugs related driver and fusion genes. The signature 15 associated with defective DNA mismatch repair (dMMR) was only identified in the CSF group. Cancer associated pathway analysis further revealed that ErbB (95%) and cell cycle (84%) were unique pathways in CSF samples. The tumor evolution analysis showed that CSF carried significantly fewer clusters, but subclonal proportion of EGFR was remarkably increased with tumor progression. Collectively, CSF sequencing showed unique genomic characteristics and the intense copy number instability associated with cell cycle disorder and dMMR might be the crucial genetic factors in BM of LUAD.

Investigation of the relationship between immune checkpoints and mismatch repair deficiency in recurrent and nonrecurrent glioblastoma

Background/aimMicrosatellite instability tests and programmed cell death-1 (PD-1)/programmed cell death ligand-1 (PD-L1) in the immune checkpoint pathway are the tests that determine who will benefit from immune checkpoint inhibitor therapy. We aimed to show the expression of DNA mismatch repair proteins and PD-1/PD-L1 molecules that inhibit immune checkpoints, to explain the relationship between them, and to demonstrate their predictive role in recurrent and nonrecurrent glioblastoma.Materials and methodsWe analyzed 27 recurrent and 47 nonrecurrent cases at our archive. We performed immunohistochemical analysis to determine expressions of PD-1, PD-L1, and mismatch repair proteins in glioblastoma. We evaluated the relationship between these two group and compared the results with the clinicopathological features.ResultsThe mean age of diagnosis was significantly lower in recurrent glioblastoma patients. Median survival was longer in this group. We found that PD-L1 expression was reduced in recurrent cases. Additionally, recurrent cases had a significantly higher rate of microsatellite instability. Loss of PMS2 was high in both group but was substantially higher in recurrent cases.ConclusionThe presence of microsatellite instability and low PD-L1 levels, which are among the causes of treatment resistance in glioblastoma, were found to be compatible with the literature in our study, with higher rates in recurrent cases. In recurrent cases with higher mutations and where immunotherapy resistance is expected less, low PD-L1 levels thought that different combinations with other immune checkpoint inhibitors can be tried as predictive and prognostic marker in GBM patients.