MMR Protein Expression Research Articles

Clinical significance of molecular classification and hereditary phenotypic characteristics in endometrial carcinoma

Objective: To analyze the clinical significance of molecular classification and hereditary phenotype in endometrial carcinoma (EC) based on high throughput sequencing (NGS). Methods: 97 EC samples were collected retrospectively from December 2019 to October 2022 in China-Japan Friendship Hospital. NGS technique was used to analyze the molecular classification, POLE hypermutation, microsatellite high Instability/mismatch repair dysfunction (MSI-H/MMRd), P53 protein abnormality (P53 abn), and non-specific molecular profile (NSMP). Lynch syndrome related genes and BRCA1/2 genes were detected by NGS and their genetic characteristics were analyzed. Results: Of the 97 EC cases, 77 were endometrial adenocarcinoma and 20 were other pathological subtypes. The proportions of the four molecular subtypes were 9.3% (9/97) POLE hypermutation, 16.5% (16/97) MSI-H, 17.5% (17/97) P53 abn and 56.7% (55/97) NSMP, respectively. There were significant differences in age, histological type, lymph node metastasis, pathological stage and other parameters among the four molecular types (P＜0.05). 8.2% (8/97) were multiple molecular typing and four multiple molecular typings detected, including POLEmut-MSI-H, POLEmut-P53abn, MSI-H-P53abn, P53abn-P53abn, which accounted for 1.0% (1/97), 3.1% (3/97), 1.0% (1/97) and 3.1% (3/97), respectively. The consistent rate of MSI-H and MMR protein expression was 92.9% (Kappa=0.818, P＜0.001). The coincidence rate between TP53 gene sequencing and P53 protein expression was 88.9% (Kappa=0.661, P＜0.001). In MSI-H type, 25.0% (4/16) were diagnosed as Lynch syndrome, and 75.0% (12/16) were diagnosed as Lynch like syndrome. 7.2% (7/97) BRCA2 somatic variation was detected, while BRCA1/2 germline variation was not detected in 97 cases. Conclusions: EC molecular classification has feasibility and clinical value. High throughput sequencing can detect low frequency mutations of TP53 gene, suggesting that it can provide more accurate molecular information and more accurate molecular typing effect. It is suggested to further detect Lynch syndrome related genes in patients with MSI-H, so as to carry out genetic management for patients and their families and achieve better therapeutic effect.

Immunohistochemical Expression of Mismatch Repair Proteins in Colorectal Carcinomas with Histopathological Correlation in a Quaternary Care Centre in South India

Background and Aims: Colorectal carcinomas are one of the most prevalent malignant neoplasms globally and are characterised by a range of genetic and epigenetic alterations, primarily chromosomal instability and microsatellite instability. This study aims to assess the expression of MMR proteins in patients with colorectal carcinoma and to examine the relationship between MMR status and various histopathological and clinical variables. Material and Methods: All biopsy and resection cases of colorectal carcinoma on which MMR was done by IHC were studied from December 2022 to November 2023. Histopathological and immunohistochemical assessments of mismatch repair proteins were done for 153 colorectal carcinoma patients in formalin-fixed paraffin-embedded tumour tissues. Statistical analysis was carried out using SPSS software (IBM, 28.0). Results: Out of 153 cases collected, 23 cases (15%) had a loss of MMR expression, and 130 cases (85%) had no loss of MMR protein. Combined loss of MLH1 and PMS2 was found in 16 cases (70%), combined loss of MSH2 and MSH6 was found in five cases (21%) and isolated loss of PMS2 was found in two cases (9%). Adenocarcinoma NOS, mucinous differentiation, medullary pattern, right-sided tumours, female gender and younger age group correlated with loss of MMR expression. Conclusion: Molecular study is the first approach for detecting MSI associated with CRC, IHC is a very good alternative to identify microsatellite instability. IHC methods can be used as a reliable tool in the workup for MSI as IHC markers (antibodies to the MMR proteins) are now easily accessible in most laboratories.

Study of Microsatellite Instability by Immunohistochemistry in a Cohort of Patients With Melanoma.

Microsatellite instability (MSI) has prognostic value and impacts therapy strategies in several malignancies. Data regarding MSI in melanoma are scarce. The aim of this study was to assess MSI through the analysis of MMR protein expression in patients with melanoma. An observational retrospective single-center study was designed based on patients with primary melanoma. We assessed MSI through immunohistochemical staining with anti-MLH1, anti-MSH2, anti-MSH6, and anti-PMS2 on full-thickness excision tissue. Ninety-three patients were included in this study. The complete absence of nuclear staining in tumoral cells was extremely rare, with only one melanoma not expressing MSH6. Most melanomas showed an expression index for MLH1 (77.7%), MSH2 (87.2%), and PMS2 (78.6%) ≥ 75%. Most melanomas (57.8%) exhibited an MSH6 expression index in the range of 1%-74%. A lowMSH6 expression index and a reduced combined MMR protein expression index (MMR-e) were significantly associated with higher melanoma-specific survival. A mildPMS2 staining intensity was significantly associated with a higher melanoma-specific survival. The patients with high MMR-e who received immunotherapy progressed and died more frequently than those with reduced MMR-e (75% vs. 33.3%). More studies are needed to further define the role of MSI in melanoma prognosis and response to immunotherapy.

P53 Abnormal (Copy Number High) Endometrioid Endometrial Carcinoma Has a Prognosis Indistinguishable From Serous Carcinoma.

Among the 4 molecular subgroups of endometrial carcinoma, the p53 abnormal (copy number high) subgroup has the worst prognosis; however, the histologic characteristics of this subgroup are not well established. Also, it is not well established whether low-grade tumors can belong to the p53 abnormal molecular subgroup and if so, what is the prognostic significance of the p53-mutated molecular subgroup in low-grade tumors. In the current study, we included 146 p53-mutated endometrial carcinomas and performed molecular subgrouping either based on a combination of immunohistochemical studies for p53 and MMR protein expression and POLE mutation testing (81 cases) or based on array-based and sequencing-based technologies (65 cases). We excluded cases that belonged to the POLE mutant or MSI molecular subgroups and only studied p53 abnormal (molecular subgroup) endometrial carcinomas (125 cases). In 71 cases, the molecular subgroup was determined by a combination of immunohistochemical studies and POLE mutation testing, and in 54 cases by array-based and sequencing-based methods. We reviewed 1 to 2 representative digital slides from each case and recorded the morphologic characteristics as well as clinical, treatment, and survival follow-up data. Overall, 47 cases were classified as endometrioid carcinoma, 55 serous carcinoma, and 23 other histotypes. Eight cases were FIGO 1, 21 were FIGO 2, and 91 were FIGO 3. A significant proportion of the cases (24.2%) were histologically classified as low-grade (FIGO 1 or 2) endometrioid carcinoma. There was no morphologic characteristic that showed prognostic implication. There was no significant difference in survival among different histotypes (P=0.60). There was no significant difference in survival among low-grade endometrioid (FIGO 1 or 2) versus high-grade (FIGO 3) tumors (P=0.98). Early-stage (stage I), low-grade tumors showed no significant survival advantage over early-stage, high-grade tumors (P=0.16) and this was more evident in FIGO 2 tumors. Although not statistically significant, the FIGO 2 tumors showed a trend toward worse survival than FIGO 3 tumors. Among the cases with available treatment data, more patients with early-stage high-grade tumors received adjuvant treatment, compared to patients with early-stage low-grade tumors, possibly explaining this trend (P=0.03). In conclusion, the findings of our study suggest that low-grade p53 abnormal endometrioid endometrial carcinomas (especially FIGO 2 tumors) have an aggressive course, with a prognosis similar to high-grade tumors. Furthermore, our study suggests that patients who had early-stage low-grade p53 abnormal disease might have been undertreated because of the "low-grade" histotype.

Validation of a one-step genomics-based molecular classifier for endometrial carcinoma in a large Chinese population

ObjectiveThe aim of this study is to delineate the molecular classification features within Chinese endometrial cancer (EC) patients and to evaluate the concurrence between two widely employed methods for diagnosing EC molecular subtypes. MethodsThis retrospective observational cohort study encompassed 479 cases of EC for analysis. Utilizing next-generation sequencing (NGS) panels targeting POLE, TP53, and microsatellite instability (MSI) status, four subtypes [POLE ultramutated (POLE mut), MMR-deficient (MMRd), p53 abnormal (p53abn), and no specific molecular profile (NSMP)] were classified. Immunohistochemistry (IHC) was employed to ascertain the expression of p53 and MMR proteins. ResultsAmong the 479 patients, the distribution of EC subtypes was as follows: 28 (5.85%) POLE mut, 67 (13.99%) MMRd, 60 (12.53%) p53abn, and 324 (67.64%) NSMP. When compared to published findings on EC subtypes in the Caucasian population, our real-world data on Chinese ECs revealed a notably higher proportion of NSMP/CNL (copy number low). The evaluation of MSI/MMR status through NGS-based and IHC-based methods displayed substantial concordance (Kappa = 0.91). Slight discordance between the two techniques in identifying p53 abnormalities (Kappa = 0.83) might stem from TP53 truncating mutations, cytoplasmic p53 expression, null TP53 mutants, and well-documented challenges in interpreting p53 IHC. ConclusionsChinese ECs exhibit distinctive molecular attributes. For accurate molecular subtyping of Chinese ECs, additional molecular markers that align with the Chinese population's characteristics should be incorporated into existing classifiers. The study's outcomes underscore a strong agreement between NGS and IHC in TP53/p53 detection and MSI assessment.

Abstract B042: Clinical and molecular characterization of Lynch syndrome-associated pancreas adenocarcinoma (PDAC)

Abstract Background: Lynch syndrome (LS) is a pan-cancer predisposition syndrome caused by pathogenic germline alterations (gPVs) in DNA mismatch repair genes (PMS2, MSH6, MLH1, MSH2, EPCAM). It is characterized by microsatellite instability (MSI)/deficient DNA mismatch repair (dMMR) of associated tumors, which predicts immune checkpoint blockade (ICB) response. Clinical and molecular features of LS-PDAC are not well defined. Herein we sought to describe clinical characteristics, MSI prevalence, and ICB response. Methods: Patients (pts) with LS-associated gPV and PDAC who had consented to IRB-approved protocol of matched tumor-normal sequencing (MSK-IMPACT from which MSIsensor status derivable) were included. MiMSI utilized to assess microsatellite stable (MSS) PDACs to account for low tumor content. MMR status defined with immunohistochemistry (IHC). Composite MSI adjudicated as either loss of MMR protein expression by IHC or MSI by MSISensor or MiMSI. FACETS algorithm assessed biallelic MMR gene alteration status. Mutational signature analysis performed on MSI tumors with deconstructSigs. Results: N=29 pts identified with LS-associated gPVs and PDAC: 10 MSH2 (34%), 9 MSH6 (31%), 7 PMS2 (24%), 2 MLH1 (7%), 1 EPCAM (3%). Majority white (24, 83%) and female (15, 52%). At diagnosis 62% pts early-stage disease (8 stage II, 10 stage III), 11 stage IV. Median age at diagnosis: 68 yrs (range 45-88). Eighteen (62%) had first-degree family history of LS spectrum cancers. Four pts had metachronous cancers (2 CRC, 1 uterine, 1 CRC and uterine). Orthogonal tumor testing feasible in 22 pts (76%). MiMSI (conducted for 16) reclassified 4 as MSI that were indeterminate by MSISensor; IHC (conducted for 15) classified 1/8 tumors as dMMR previously MSS on MSISensor. Whole cohort MSI status: 16 composite MSI (59%), 11 MSS (41%), and 2 MS unknown. gPVs in N= 16 with MSI tumors: 9 MSH2, 4 MSH6, 2 MLH1, and 1 PMS2; amongst N= 11 MSS tumors: 6 gMSH6, 4 gPMS2, and 1 EPCAM. Amongst 24 evaluable pts biallelic loss identified in 6 pts with MSI disease. The dominant mutational signature in 4/6 was Clock/aging and not MSI; 2 of these 4 harbored gMSH2, and 2/4 gMSH6. KRAS and TP53 mutations more common in sporadic MSS PDAC than LS-PDAC (p=0.001, p=0.005 respectively); KRAS G12R was enriched in LS PDAC vs sporadic PDAC (31.6% vs 15.3%, p=0.06). N= 13 (47%) received ICB, inclusive of 4 reclassified by MiMSI and 8 with metastatic disease. In evaluable pts with MSI disease, overall response rate 60% (2 CR, 4 PR, 4 SD). N= 1 MSS PDAC had POD as best response. Median ICB duration: 27.7 months (95% CI 9.0, NR). Conclusion: In this LS PDAC cohort we observed a higher proportion of MSH6, MSH2, PMS2 gPVs relative to other cohorts. LS-PDAC MSI arises frequently in association with gMSH2, gMLH1. MSI status determination with orthogonal testing is critical to appropriately select pts for ICB. Outcome to ICB in LS PDAC MSI comparable to other tumor types highlighting the importance of MSI as a predictive biomarker in PDAC. Citation Format: Emily Harrold, Catherine A. O'Connor, David Lin, Andrea Gazzo, Henry Walch, Megha Ranganathan, Amanda Catchings, Sarah Kane, Fergus Keane, Deborah M. Thurtle-Schmidt, Fiyinfolu Balogun, Anna Varghese, Kenneth Yu, David Kelsen, Alicia Latham, Britta Weigelt, Wungki Park, Zsofia Stadler, Eileen M. O'Reilly. Clinical and molecular characterization of Lynch syndrome-associated pancreas adenocarcinoma (PDAC) [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Pancreatic Cancer; 2023 Sep 27-30; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(2 Suppl):Abstract nr B042.

Tumor-infiltrating lymphocytes, PD-L1, and MMR-deficiency combined characterization may identify subgroups of rectal cancer patients who would benefit from immunotherapy

IntroductionMismatch repair deficiency, immunological fertility, and PD-L1 expression status are key histopathological and molecular features defining tumor responsiveness to immunotherapy and, eventually, prognosis. These were investigated in a series of locally advanced rectal cancer patients treated with postoperative chemotherapy and radiotherapy. Materials and methodsTumor-infiltrating lymphocyte (TIL) density was assessed in hematoxylin-eosin tissue sections. PD-L1 expression and the expression of MMR proteins (MLH1, PSM2, MSH2, and MSH6) were assessed with immunohistochemistry. Their association with histopathological variables (node involvement and tumor budding) and prognosis was assessed. ResultsThe TIL-density was significantly higher in the invading tumor front and was inversely related to tumor budding and directly with better overall survival (OS) and distant metastasis-free survival (DMFS) (p = 0.02 and 0.02, respectively). Cancer cell PD-L1 expression was related to high TIL-density (p < 0.01) but not to prognosis, although its overexpression defined a trend for poorer OS in patients with high TIL-density. High PD-L1 expression by stroma infiltrating immune cells was linked with better OS and DMFS (p = 0.007 and 0.001, respectively. MMR deficiency was recorded in 26.2 % of cases, and this was linked with higher TIL-density, but not with prognosis. ConclusionsDense intratumoral lymphocytic infiltration relates to a better prognosis in rectal cancer, although it is also linked with PD-L1 expression that may adversely modulate the anti-tumor effects of TILs. This latter subgroup of patients (high TIL-density/high cancer cell PD-L1 expression) could be an additional target for anti-PD-1/PD-L1 immunotherapy, along with the established subgroup of MMR deficient patients.

A retrospective study of consistency between immunohistochemistry and polymerase chain reaction of microsatellite instability in endometrial cancer.

Identification of endometrial cancers (EC) with mismatch repair deficiency (dMMR) or microsatellite instability-high (MSI-H) is essential for Lynch syndrome screening and treatment stratification. We aimed to assess the utility of immunohistochemistry (IHC) staining for MMR protein expression and polymerase chain reaction (PCR)-based MSI assays in EC and the correlation between MMR/MSI status and various clinicopathological parameters. We reviewed the clinical and pathological information of 333 patients with EC. MMR protein expression was assessed as retained or lost to determine MMR status by IHC staining, and MSI status was identified by PCR capillary electrophoresis (PCR-CE) testing with a National Cancer Institute (NCI) panel. The correlation of MMR/MSI status with clinicopathological features was determined by statistical analysis. Discrepant results were further analyzed using an alternative PCR-CE MSI (Promega panel) method, MLH1 promoter methylation assays, and next-generation sequencing (NGS). Among the EC patients, the overall percentage of dMMR was 25.2%, and the overall percentage of MSI-H was 24%. Among the dMMR patients, 50 (59.5%) showed loss of MLH1 and PMS2 expression, 19 (22.6%) loss of MSH2 and MSH6 expression, and seven (8.3%) and eight (9.5%) loss of PMS2 and MSH6 expression, respectively. The dMMR subgroup was significantly younger than the pMMR subgroup, especially for <60-years-old patients (p=0.038). In addition, we identified a strong correlation between MMR/MSI status and high-grade endometrioid or nonendometrioid components (p=0.004 or p=0.003). IHC staining and PCR-CE assay results showed a high level of overall concordance (98.8%, Cohen's κ=0.98). Four patients were found to have dMRR/MSS in both examinations. We reanalyzed them with additional methods. One case showed MLH1 promotor methylation, and the other three cases harbored MSH6 germline pathogenic variations. One of the cases with MSH6 deficiency was reanalyzed as MSI-H by alternative PCR-CE assay or NGS testing. This study indicates that the combined use of MMR-IHC and PCR-CE MSI analyses may effectively avoid misdiagnoses of EC patients with dMMR/MSI-H. However, use of PCR-CE alone to evaluate MMR/MSI status may lead to missed diagnosis, especially for EC patients with MSH6 deficiency and presenting MSS.

Exploring the Expression and Prognosis of Mismatch Repair Proteins and PD-L1 in Colorectal Cancer in a Chinese Cohort.

Exploring the expression and prognosis of mismatch repair proteins and PD-L1 in colorectal cancer. A total of 272 patients with surgically resected CRC were enrolled in the study from January 2018 to May 2022 at Nanjing Drum Tower Hospital (The Affiliated Hospital of Nanjing University Medical School). Surgically resected samples were collected from patients along with general, clinicopathological, and imaging data for each patient. Immunohistochemistry (IHC) was used to detect expression of MSH2, MSH6, MLH1, and PMS2 proteins in tumor tissue. X-squared (X2) testing was performed to investigate the correlation between expression of MMR proteins and PD-L1 in CRC tumor tissues and clinicopathological characteristics. Correlation analysis was also used to compare the deletion of four MMR proteins in CRC tumor tissues. A survival curve and Log rank test were used to investigate the relationship between the expression of MMR proteins and PD-L1 with regard to CRC patient prognosis and survival. MMR protein expression deletion was correlated with tumor location, the degree of tissue differentiation, and TNM stage (P<0.05). PD-L1 expression was correlated with TNM stage (P<0.05). Correlation analysis of deletion of MMR protein isoform expression found that PMS2 deletion was significantly correlated with MLH1 deletion (P<0.05). Similarly, MSH2 deletion was significantly correlated with MSH6 deletion (P<0.05). PMS2 deletion was also found to be correlated with PD-L1 expression (P<0.05). Progression-free survival was found to be significantly longer in mismatch repair-proficient (pMMR) patients compared with mismatch repair-deficient (dMMR) patients. Deletion of MMR proteins and expression of PD-L1 are closely related to clinicopathological characteristics and overall prognosis of CRC patients. This suggests the relevance of MMR and PD-L1 as potential biomarkers for treatment of CRC patients.

Tuberous sclerosis complex mutations in patients with pancreatic neuroendocrine tumors. Observations on phenotypic and treatment-related associations.

Pancreatic neuroendocrine tumors (PanNETs) in familial tuberous sclerosis (TSC1 and TSC2 mutations) have been known and studied. However, little is known about PanNET patients harboring the very rare (less than 2%) sporadic TSC mutations. Some renal tumors have been shown to harbor sporadic TSC mutations, with a distinctive morphological correlate. We hereby describe this rather unusual molecular alteration in well-differentiated pancreatic neuroendocrine tumors (WD PanNETs) with a focus on their morphology and treatment outcomes. Six cases of WD PanNETs harboring sporadic TSC mutations were identified retrospectively. H&E slides and corresponding immunostains were reviewed for all cases. Clinical, molecular, and radiological information was obtained using the electronic medical records. Cohort consisted of 4 males and 2 females. Median age at diagnosis was 50years (range 33-74years). Origin of neoplasm was the pancreas and, in all but one, patient had liver metastasis by the time of presentation. Six out of six cases demonstrated a unique tumor morphology, with ample eosinophilic cytoplasm. Tumors were arranged in sheets and nests; prominent cystic change was noted in one case. Two cases were additionally biopsied post-treatment with capecitabine and temozolomide, and showed even more abundant oncocytic cytoplasm, eccentric nuclei, and a prominent cherry red nucleolus, and were arranged in a cluster of 3-4 cells, separated by stromal cells. Every patient had a different TSC2 variant with no cases of TSC1 mutations. Other common variants included MEN1 (4/6), DAXX (2/6), and TP53 (2/6). Per the WH0 2019 classification, tumors were graded as NET-G3 (n = 3) and NET-G2 (n = 3). Ki-67s ranged from 7.2 to 60. All cases had retained MMR protein expression. The majority of patients (4/6) have expired. Although they received multiple treatments, a consistent pattern observed in patients was marked radiologic response to chemotherapy with capecitabine and temozolomide (offered in 5/6 patients) with duration of responses reaching 11months in the majority of cases, with one patient showing near complete pathologic response of localized disease. TSC2 mutations may confer distinctive appearance in WD PanNETs, reminiscent of their effects in renal tumors. Although not entirely specific, this distinct morphological pattern with abundant eosinophilic cytoplasm in WD PanNETs could be reflective of an associated TSC mutation, with suggestions of significant therapeutic response to a specific cytotoxic chemotherapy.

Microsatellite instability in non-endometrioid ovarian epithelial tumors: a study of 400 cases comparing immunohistochemistry, PCR, and NGS based testing with mutation status of MMR genes

Testing of microsatellite instability is not only used as a triage for possible Lynch syndrome, but also to predict immunotherapy treatment response. The aim of this study was to assess the frequency of mismatch repair deficiency (MMR-D) / microsatellite instability (MSI) in 400 cases of non-endometrioid ovarian tumors (high-grade serous, low-grade serous, mucinous and clear cell), to compare different methodological approaches of testing, and to assess the optimal approach for next generation sequencing (NGS) MSI testing. For all tumors, we evaluated immunohistochemical (IHC) expression of MMR proteins and assessed microsatellite markers by PCR-based method. Except for high-grade serous carcinoma, we correlated the findings of IHC and PCR with NGS-based MSI testing. We compared the results with somatic and germline mutation in MMR genes. Among the whole cohort, seven MMR-D cases, all clear cell carcinomas (CCC), were found. On PCR analysis, six cases were MSI-high and one was MSS. In all cases, mutation of an MMR gene was found; in two cases, the mutation was germline (Lynch syndrome). An additional five cases with a mutation in MMR gene(s) with MSS status and without MMR-D were identified. We further utilized sequence capture NGS for MSI testing. Employing 53 microsatellite loci provided high sensitivity and specificity. Our study shows that MSI occurs in 7% of CCC while it is rare or absent in other non-endometrioid ovarian neoplasms. Lynch syndrome was present in 2% of patients with CCC. However, some cases with MSH6 mutation can evade all testing methods, including IHC, PCR, and NGS-MSI.

Investigation of the Relationship Between Immunohistochemical Mismatch Repair (MMR) Protein Expression and Prognostic Parameters in Endometrial Carcinomas

Objective: Molecular classification has been the most important development in endometrial carcinomas in recent years. This classification divides tumors into four groups: (i) POLE mutant group, (ii) microsatellite instable (MSI) group, (iii) high copy number group (P53 mutation), and (iv) low copy number group. Among these groups, POLE and MSI groups stand out with their better prognosis and potential to benefit from immune-control inhibitor therapy. In our study, we aimed to compare the prognostic parameters of patients with and without nuclear expression loss in MMR proteins (MLH-1, PMS-2, MSH-2, MSH-6) by immunohistochemical (IHC) method. Methods: Between 2017 and 2020, 80 patients who were diagnosed with endometrial carcinoma in hysterectomy material and whose MMR proteins were evaluated as IHC were included in the study. Patients with and without MMR loss were compared in terms of tumor size, histological grade (HD), depth of myometrial invasion, lymphovascular invasion (LVI), and cervical involvement. Results: Loss of any of the MMR proteins was present in 37 cases (46.3%), while 43 cases (53.7%) had no loss. When the cases were compared in terms of loss of MMR protein nuclear expression, 45.9% (17/37) of the cases with loss and 27.9% (12/43) of the cases without loss had histologic grade III (P = 0.03). There was no statistically significant difference between the two groups in terms of myometrium 1/2 external invasion, cervical stromal involvement, and LVI. Conclusion: Approximately half of the patients in our study lost at least one of the MMR proteins. The most common losses were MLH-1 and PMS-2. The HD of patients with loss of nuclear expression of MMR proteins tended to be statistically significantly higher than those without loss.

Microsatellite Instability and P53 Aberrant Expression in Gastric Adenocarcinoma: Immunohistochemical Assessment and Correlation with Clinico-pathological Characteristics

Background: Gastric cancer (GC) is among the five most frequent cancer worldwide, following lung, breast, colorectal, and prostate cancer. It is the 12th most prevalent cancer in both sexes in Egypt, accounting for 1.6% of all malignancies. Distinct molecular subtypes of gastric adenocarcinoma (e.g., microsatellite instable subtype and P53 aberrant subtype) have been reported by different classification systems. However, the relation of these molecular subtypes to different clinicopathological features is still controversial.&#x0D; Aim of the Work: To utilize the immunohistochemical expression of DNA MMR proteins (MLH1 and MSH2) and p53 to detect microsatellite unstable and P53 aberrant molecular types in gastric adenocarcinoma. Moreover, to correlate immunohistochemically detected microsatellite unstable and P53 aberrant molecular types of gastric carcinoma with different clinicopathological characteristics.&#x0D; Materials and Methods: The immunohistochemical expression of MLH1, MSH2 and P53 proteins was evaluated in 70 cases of gastric adenocarcinoma.&#x0D; Results: Microsatellite status/Mismatch repair status showed a statistically significant relation with WHO classification, tumor differentiation, lymph node status, and TNM staging. P53 aberrant type showed a statistically significant relation with tumor differentiation, depth of tumor invasion, lymph node status, and TNM staging.&#x0D; Conclusions and Recommendations: Microsatellite instable GC and P53 aberrant GC are two distinct molecular subtypes of gastric adenocarcinoma with distinct clinicopathological features and different prognostic outcomes. Microsatellite instable tumors are associated with good prognostic parameters while, P53 aberrant tumors are associated with poor prognostic parameters. Both subtypes could be detected using immunohistochemistry and could represent potential targets for future therapeutic agents.

Efficacy and safety of neoadjuvant preoperative short-course radiation followed by envafolimab plus CAPEOX in microsatellite stable (MSS)/mismatch repair proficient (pMMR) locally advanced rectal cancer.

134 Background: Chemoradiation is the standard neoadjuvant treatment for locally advanced rectal cancer. Microsatellite stable (MSS)/ mismatch repair proficient (pMMR) rectal cancer rarely responds to immune checkpoint inhibitor monotherapy, but combination with chemoradiation may improve sensitivity of MSS/pMMR tumors by inducing immune-stimulatory effects. Therefore, we aimed to investigate the efficacy and safety of patients treated with neoadjuvant preoperative short-course radiation followed by envafolimab plus CAPEOX for MSS/pMMR locally advanced rectal cancer. Methods: This is an open-label, single-center, phase ¢ò study. Patients (pts) with locally advanced rectal adenocarcinoma with MSS/pMMR were eligible. MMR protein expression was tested by immunohistochemistry (IHC) £¬and MSI status was confirmed by NGS (next generation sequencing). All pts included in this study underwent neoadjuvant short-course radiation (total dose of 5¡Á5Gy) in the first week after enrollment, then followed by 6 cycles of envafolimab (anti-PD-L1 inhibitor,150mg, d1, subcutaneous injection, QW) plus 2 cycles of CAPEOX in the next six weeks, and subsequently underwent total mesorectal excision (TME) in the ninth week. The primary endpoint is pathological complete response rate. Secondary endpoints include tumor regression grade (TRG), 3 year disease free survival, overall survival, toxicity, and quality of life (QoL). Results: This study intends to recruit 32 pts, and a total of 21 pts were enrolled from January 2022 to September 2022. Overall median age was 67 (42-79) years. 12 pts completed study designed treatment protocol (envafolimab plus CAPOX) followed with TME procedures, and 9 pts are still undergoing neoadjuvant treatment. All 12 pts achieved major partial response (MPR) evaluated by diffusion-weighted magnetic resonance imaging (DW-MRI), and 8 pts (8/12,76.6%) achieved pCR. During neoadjuvant treatment period, 20 pts (20/21, 95.2%) presented with treatment-related AEs (TRAEs) of any grade, 18 pts (18/21, 85.7%) had grade 1-2 and one each pts had grade 3 and 4 thrombocytopenia (2/21, 9.5%). The most common TRAEs were sensation of rectal tenesmus. Conclusions: Neoadjuvant preoperative short-course radiation followed by envafolimab plus CAPEOX in MSS/pMMR locally advanced rectal cancer achieved a promising pathologic response. Meanwhile, this combination neoadjuvant therapy is safe and worthy of application to clinical practice. (Funded by Sir Run Run Shaw Hospital Zhejiang University School of Medicine.) Clinical trial information: NCT05216653 .

Are mismatch repair deficient endometrial cancer recurrences more salvageable than intact cohort? (272)

Are mismatch repair deficient endometrial cancer recurrences more salvageable than intact cohort? (272)

Disparities in completion of genetic testing and counseling for Lynch syndrome in high-risk patients diagnosed with endometrial cancer (601)

Disparities in completion of genetic testing and counseling for Lynch syndrome in high-risk patients diagnosed with endometrial cancer (601)

Molecular classification of endometrial cancer of Chinese population.

e17623 Background: Endometrial cancer (EC) is one of the most prevalent gynecologic tumors. Current diagnosis and treatment of EC no longer rely solely on traditional histopathological classification. Nevertheless, molecular classification of EC demonstrated clear prognostic value and may guide clinical decision. Methods: In this study, archived tissue specimens from 240 EC patients from Department of Pathology, Peking University People’s Hospital. Four subtypes [POLE ultramutated (POLE mut), microsatellite instability high (MSI-H), copy number low (CNL), and copy number high (CNH)] were stratified by next-generation sequencing (NGS) panel (Amoy Diagnostics, Xiamen, China) targeting POLE, TP53, BRCA1, and BRCA2 genes and microsatellite instability (MSI) status. Immunohistochemistry (IHC) was applied to detect the expression of P53, MMR and other related proteins. Results: Distribution of the EC subtypes in 240 patients was 13 (5.42%) of POLE mut, 36 (15.00%) of MSI-H, 41 (17.08%) of CNH, and 150 (62.50%) of CNL. Compared to published results of EC subtypes in Caucasian including TCGA, ProMisE as well as TransPORTEC, real-world data on Chinese ECs displayed a significantly larger proportion of CNL. In addition, novel biomarkers such as DUSP1, MCF7 and BUB1, which were independent prognostic marker from our previous research were validated. Also, it was found that BRCA2 appeared to be more prevalent in EC than BRCA1. Further analysis revealed that the overall consistency for NGS-based and IHC-based TP53 abnormalities detection and MSI/MMR status assessment were as high as 87.5% and 100%, respectively. Conclusions: Chinese ECs have unique molecular characteristics. In order to perform accurate molecular typing of Chinese ECs, more molecular indicators that match the characteristics of the Chinese population need to be added to the existing classifiers. NGS-based panel is easy to operate and replicate with high accuracy. Thus, it is a viable alternative to IHC in EC molecular classification.

Prognostic Impact of Tumor Budding on Moroccan Colon Cancer Patients.

Background Tumor budding is now emerging as one of the robust and promising histological factors that play an important role in colon cancer. In this study, we aimed to investigate the association between tumor budding and tumor clinicopathological factors, tumor molecular signature, and patient survival for the first time in a Moroccan population. Methods We collected data of 100 patients operated from colon adenocarcinoma. Tumor budding was assessed on HES slides, according to the International Tumor Budding Consensus Conference 2016 recommendations. The expression of MMR proteins was performed by immunohistochemistry. KRAS and NRAS mutations testing was performed by Sanger sequencing and pyrosequencing. Results High tumor budding grade (BUD 3) was found to be significantly associated with adverse clinicopathological features including older age (P=0.03), presence of perineural invasion (P=0.02), presence of vascular invasion (P=0.05), distant metastases (P < 0.001), advanced TNM stage (P=0.001), the occurrence of relapse (P=0.04), and the high number of deceased cases (P=0.02). Interestingly, we found that tumors with high-grade tumor budding were more likely to be microsatellite stable (MSS) (P=0.005) and harbor more KRAS mutations (P=0.02). Tumors with high-grade tumor budding were strongly associated with KRAS G12D mutation (P=0.007). In all stages, high tumor budding was correlated with poorer overall survival (P=0.04) and decreased relapse-free survival with a difference close to significance ((P=0.09). We concluded that high tumor budding was strongly associated with unfavorable clinicopathological features and special molecular biomarkers and effectively affects the overall survival of CC patients. Conclusions Based on these findings and the ITBCC group recommendations, tumor budding should be taken into account along with other clinicopathologic factors in the risk assessment of colorectal cancer.

Frequency and clinical features of deficient mismatch repair in ovarian clear cell and endometrioid carcinoma.

ObjectiveTo clarify the frequency of deficient mismatch repair (dMMR) in Japanese ovarian cancer patients, we examined microsatellite instability (MSI) status and immunohistochemistry (IHC) subtypes, including endometrioid carcinoma (EMC), clear cell carcinoma (CCC), or a mixture of both (Mix).MethodsWe registered 390 patients who were diagnosed with EMC/CCC/Mix between 2006 and 2015 and treated at seven participating facilities. For 339 patients confirmed eligible by the Central Pathological Review Board, MSI, IHC, and MutL homolog 1 methylation analyses were conducted. The tissues of patients with Lynch syndrome (LS)-related cancer histories, such as colorectal and endometrial cancer, were also investigated.ResultsMSI-high (MSI-H) status was observed in 2/217 CCC (0.9%), 10/115 EMC (8.7%), and 1/4 Mix (25%). Additionally, loss of MMR protein expression (LoE-MMR) was observed in 5/219 (2.3%), 16/115 (14.0%), and 1/4 (25%) patients with CCC, EMC, and Mix, respectively. Both MSI-H and LoE-MMR were found significantly more often in EMC (p<0.001). The median (range) ages of patients with MMR expression and LoE-MMR were 54 (30–90) and 46 (22–76) (p=0.002), respectively. In the multivariate analysis, advanced stage and histological type were identified as prognostic factors.ConclusionThe dMMR rate for EMC/CCC was similar to that reported in Western countries. In Japan, it is assumed that the dMMR frequency is higher because of the increased proportion of CCC.

Immunohistochemical analysis of Mismatch repair-deficient gene expression in unselected Colorectal Cancer: An update of tertiary cancer center from North India

Colorectal cancer (CRC) is the third most deadly and fourth most commonly diagnosed cancer in the world. The present study has been carried out to see the frequency of lost MMR protein expression and its histopathological characteristics in unselected colorectal cancer patients from north India. 103 consecutive patients of colorectal cancer who underwent surgery between 2014-2018 in a tertiary care teaching hospital in North India were included in the study. The study was approved by the Institute’s Ethical Committee. MMR protein status was determined by Immunohistochemistry (IHC) to examine the expression of MLH1, PMS2, MSH2 and MSH6 on paraffin-embedded tissues. Patients with MLH1deficient protein were further followed by BRAF V600E testing. The histopathological features were correlated with MMR protein expression. IHC results revealed a loss of different MMR protein expression in 33 (32%) patients. the most frequent loss was lost MSH2 12(36.4%) followed by MLH1 10(30.3%), PMS2 8(24.2%) and MSH6 3(9.1%); Out of 10 MLH1 deficient cases, 6 (60%) were BRAF V600E mutant and 4 (40%) were BRAF-wild-type. We have found significance with medullary histological phenotype, poor histological grade and TILS. In our study, the frequency of MMR protein loss was found in 32% of patients of CRC. The loss was significantly associated with medullary phenotype, degree of differentiation and presence of tumor infiltrating lymphocytes (TILS).