Mismatch repair deficiency is rare in bone and soft tissue tumors.

INTRODUCTION: There has been an increased demand for mismatch repair (MMR) status testing in sarcoma patients after the success of immune checkpoint inhibition (ICI) in MMR deficient tumors. However, data on MMR deficiency in bone and soft tissue tumors is sparse, rendering it unclear if routine screening should be applied. Hence, we aimed to study the frequency of MMR deficiency in bone and soft tissue tumors after we were prompted by two (potential) Lynch syndrome patients developing sarcomas. METHODS: Immunohistochemical expression of MLH1, PMS2, MSH2 and MSH6 was assessed on tissue micro arrays (TMAs), and included 353 bone and 539 soft tissue tumors. Molecular data was either retrieved from reports or microsatellite instability (MSI) analysis was performed. In MLH1 negative cases, additional MLH1 promoter hypermethylation analysis followed. Furthermore, a systematic literature review on MMR deficiency in bone and soft tissue tumors was conducted. RESULTS: Eight MMR deficient tumors were identified (1%), which included four leiomyosarcoma, two rhabdomyosarcoma, one malignant peripheral nerve sheath tumor and one radiation-associated sarcoma. Three patients were suspected for Lynch syndrome. Literature review revealed 30 MMR deficient sarcomas, of which 33% were undifferentiated/unclassifiable sarcomas. 57% of the patients were genetically predisposed. CONCLUSION: MMR deficiency is rare in bone and soft tissue tumors. Screening focusing on tumors with myogenic differentiation, undifferentiated/unclassifiable sarcomas and in patients with a genetic predisposition / co-occurrence of other malignancies can be helpful in identifying patients potentially eligible for ICI.

Interpretation of Mismatch Repair Protein Immunohistochemistry in Endometrial Carcinoma Should Consider Both Lynch Syndrome Screening and Immunotherapy Susceptibility: An Illustrative Case Report.

We present an instructive case of FIGO grade 1 endometrioid endometrial carcinoma with a biphasic morphology, corresponding to subclonal loss of mismatch repair proteins (MMRP) MLH1 and PMS2 by immunohistochemistry and subclonal microsatellite instability. A pulmonary metastasis represented only the tumor component with retention of MMRPs. This case illustrates the need for pathologists to recognize and report heterogenous expression of MMRPs in endometrial carcinoma, to consider tumor heterogeneity when selecting foci for molecular studies, and to re-evaluate MMRP expression in tumor metastases, when clinically indicated. These considerations are particularly important as the relevance of MMRP expression in endometrial cancer expands beyond Lynch syndrome screening, into a new role as a predictive marker for immunotherapy.

Correlation of MLH1 polymorphisms, survival statistics, in silico assessment and gene downregulation with clinical outcomes among breast cancer cases.

This study aimed to investigate the role of MLH1 polymorphisms, respective protein structure prediction, survival analysis, related clinicopathological details and MLH1 expression in breast cancer (BC). Genotyping of selected SNPs in BC patients (493) and age matched controls (387) were performed by Tetra-ARMS PCR. Gene expression among breast tumors (127) and adjacent control tissues were analysed using reverse transcriptase PCR (RT-PCR) and immunohistochemistry. Statistical analysis was performed by SPSS and MedCalc. Conditional logistic regression analysis was applied to compute the odds ratio and confidence interval. Phyre2 and I-TASSER were used to generate MLH1 protein structures and verified by a variety of computational tools. Genotyping illustrated that MLH1 polymorphisms (rs63749795 and rs63749820) were significantly associated (P ≤ 0.05) with risk of developing BC. Down regulation of MLH1 gene expression/loss of the MLH1 protein (OR 12; CI 2.8-53.1) was observed in BC cases, illustrating its potential role in disease development. Moreover, loss of the MLH1 protein was found to be associated with higher grade cancer (P = 0.02) and lymph node positivity (P = 0.03), highlighting its essential role, as a component of the mismatch repair (MMR) machinery. Bioinformatics analysis confirmed that nonsense mutations produce a truncated MLH1 protein, causing a reduction in MMR efficiency. No association between MLH1 polymorphisms and overall and progression free survival statistics was observed among BC cases, possibly due to short follow-up study. Results at DNA, RNA and protein levels, along with in silico analysis, highlights the potential role of MLH1 in DNA repair mechanisms, within BC. Therefore, it was concluded that MLH1 may contribute towards BC development and progression.

[Comparison of the mismatch repair deficiency of colorectal cancers between African and European cohorts]. / Comparaison du « deficit mismatch repair ¼ des cancers colorectaux entre des cohortes africaines et européennes.

INTRODUCTION: According to European and American series, up to 20% of colorectal cancers are characterised by instability at microsatellites sites. MMR deficient colorectal cancers are predominantly found in the right colon. Although an increasing rate of colorectal cancer has been observed in many low-income countries including in West-Africa, data on epidemiology and biology of colorectal cancer in native Africans from this region are scarce. MATERIALS AND METHODS: We aimed to study the incidence of MMR deficiency in Côte d'Ivoire and to compare the data with those from a tertiary center in Belgium. Immunohistochemistry for MLH1, MSH2, MSH6 and PMS2 was performed on paraffin-embedded tissue samples from 83 colorectal cancers (46% males) operated in Abidjan and from 343 colorectal cancers (53% males) from Brussels. RESULTS: Colorectal cancer was occuring at a younger age in Côte d'Ivoire compared to Belgium (median age: 53 versus 66). MMR deficiency was detected in 11,7% of Belgian cases and in 13,3% of Ivorian cases. Whereas MMR deficient cancers in Brussels were mainly found in women (24/40 i.e. 60%), in Abidjan only 3/11 (27%) were female. Moreover, the predominant location of MMR deficient tumours was different between both series: in Brussels, mainly located in the right colon (24/40 i.e. 60%) whereas in Abidjan predominantly (10/11 i.e. 91%) in the left colon. In Brussels we observed in the majority of cases (67,5%) loss of expression of MLH1 and PMS2, in Abidjan loss of expression of MSH2 and MSH6 (54,5%). CONCLUSIONS: Our pilot study reveals differences in presentation of MMR deficient colorectal cancer between the two geographic regions suggesting differences in epidemiology and biology of colorectal cancer in native Africans.

Prevalence of Microsatellite Instability in Intraductal Papillary Mucinous Neoplasms of the Pancreas.

Microsatellite instability (MSI) caused by mismatch repair deficiency (dMMR) is detected in a small proportion of pancreatic ductal adenocarcinomas (PDACs). dMMR and MSI have been associated with responses of metastatic tumors, including PDACs, to immune checkpoint inhibitor therapy. We performed immunohistochemical analyses of a 445 PDAC specimens, collected from consecutive patients at multiple centers, to identify those with dMMR, based on loss of mismatch repair proteins MLH1, MSH2, MSH6, and/or PMS2. We detected dMMR in 1.6% of tumor samples; we found dMMR in a larger proportion of intraductal papillary mucinous neoplasms-related tumors (4/58, 6.9%) than non- intraductal papillary mucinous neoplasms PDAC (5/385, 1.3%) (P = .02). PDACs with dMMR contained potentially immunogenic mutations because of MSI in coding repeat sequences. PDACs with dMMR or MSI had a higher density of CD8+ T cells at the invasive front than PDACs without dMMR or MSI (P = .08; Fisher exact test). A higher proportion of PDACs with dMMR or MSI expressed the CD274 molecule (PD-L1, 8/9) than PDACs without dMMR or MSI (4/10) (P = .05). Times of disease-free survival and overall survival did not differ significantly between patients with PDACs with dMMR or MSI vs without dMMR or MSI. Studies are needed to determine whether these features of PDACs with dMMR or MSI might serve as prognostic factors.

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.

Clinicopathological characteristics of patients with upper urinary tract urothelial cancer with loss of immunohistochemical expression of the DNA mismatch repair proteins in universal screening.

OBJECTIVES: To assess the detection rate of putative Lynch syndrome-associated upper urinary tract urothelial cancer among all upper urinary tract urothelial cancers and to examine its clinicopathological characteristics. METHODS: A total of 143 patients with upper urinary tract urothelial cancer who had received total nephroureterectomy were immunohistochemically stained for the expression of mismatch repair proteins MLH1, PMS2, MSH2 and MSH6. For all suspected mismatch repair-deficient cases, MMR genetic testing was recommended and clinicopathological features were examined. RESULTS: Loss of mismatch repair proteins was found in seven patients (5%) who were thus categorized as putative Lynch syndrome-associated upper urinary tract urothelial cancer. Five of these patients showed dual loss of MSH2/MSH6. Two patients were confirmed to be MSH2 germline mutation carriers. Histologically, all seven tumors were low-grade atypical urothelial carcinoma and showed its unique histological features, such as an inverted papilloma-like growth pattern and a villous to papillary structure with mild stratification of tumor cells. Six tumors had no invasion of the muscularis propria. No recurrence or cancer-related deaths were reported in these seven patients. Just three patients met the revised Amsterdam criteria. CONCLUSIONS: This is the first report that universally examined mismatch repair immunohistochemical screening for upper urinary tract urothelial cancers. The prevalence (5%) of putative Lynch syndrome-associated upper urinary tract urothelial cancers is much higher than we had expected. We ascertained that putative Lynch syndrome-associated upper urinary tract urothelial cancers were clinically in the early stage and histologically classified into low-grade malignancy with its characteristic pathological features. The clinicopathological characteristics that we found in the present study could become additional possible markers in the diagnosis of Lynch syndrome-associated upper urinary tract urothelial cancers.

Clinicopathological and molecular features of sessile serrated adenomas with dysplasia or carcinoma.

OBJECTIVE: Sessile serrated adenomas (SSAs) are the precursors of at least 15% of colorectal carcinomas, but their biology is incompletely understood. We performed a clinicopathological and molecular analysis of a large number of the rarely observed SSAs with dysplasia/carcinoma to better define their features and the pathways by which they progress to carcinoma. DESIGN: A cross-sectional analysis of 137 SSAs containing regions of dysplasia/carcinoma prospectively collected at a community GI pathology practice was conducted. Samples were examined for BRAF and KRAS mutations, the CpG island methylator phenotype (CIMP) and immunostained for MLH1, p53, p16, ß-catenin and 0-6-methylguanine DNA methyltransferase (MGMT). RESULTS: The median polyp size was 9 mm and 86.5% were proximal. Most were BRAF mutated (92.7%) and 94.0% showed CIMP. Mismatch repair deficiency, evidenced by loss of MLH1 (74.5%) is associated with older age (76.7 versus 71.0; p<0.0029), female gender (70% versus 36%; p<0.0008), proximal location (91% versus 72%; p<0.02), CIMP (98% versus 80%; p<0.02) and lack of aberrant p53 (7% versus 34%; p<0.001) when compared with the mismatch repair-proficient cases. Loss of p16 (43.1%) and gain of nuclear ß-catenin (55.5%) were common in areas of dysplasia/cancer, irrespective of mismatch repair status. CONCLUSIONS: SSAs containing dysplasia/carcinoma are predominantly small (<10 mm) and proximal. The mismatch repair status separates these lesions into distinct clinicopathological subgroups, although WNT activation and p16 silencing are common to both. Cases with dysplasia occur at a similar age to cases with carcinoma. This, together with the rarity of these 'caught in the act' lesions, suggests a rapid transition to malignancy following a long dwell time as an SSA without dysplasia.

Sessile serrated adenomas with dysplasia: morphological patterns and correlations with MLH1 immunohistochemistry.

Sessile serrated adenomas are the precursor polyp of approximately 20% of colorectal carcinomas. Sessile serrated adenomas with dysplasia are rarely encountered and represent an intermediate step to malignant progression, frequently associated with loss of MLH1 expression. Accurate diagnosis of these lesions is important to facilitate appropriate surveillance, particularly because progression from dysplasia to carcinoma can be rapid. The current World Health Organization classification describes two main patterns of dysplasia occurring in sessile serrated adenomas, namely, serrated and conventional. However, this may not adequately reflect the spectrum of changes seen by pathologists in routine practice. Furthermore, subtle patterns of dysplasia that are nevertheless associated with loss of MLH1 expression are not encompassed in this classification. We performed a morphological analysis of 266 sessile serrated adenomas with dysplasia with concurrent MLH1 immunohistochemistry with the aims of better defining the spectrum of dysplasia occurring in these lesions and correlating dysplasia patterns with MLH1 expression. We found that dysplasia can be divided morphologically into four major patterns, comprising minimal deviation (19%), serrated (12%), adenomatous (8%) and not otherwise specified (79%) groups. Minimal deviation dysplasia is defined by minor architectural and cytological changes that typically requires loss of MLH1 immunohistochemical expression to support the diagnosis. Serrated dysplasia and adenomatous dysplasia have distinctive histological features and are less frequently associated with loss of MLH1 expression (13 and 5%, respectively). Finally, dysplasia not otherwise specified encompasses most cases and shows a diverse range of morphological changes that do not fall into the other subgroups and are frequently associated with loss of MLH1 expression (83%). This morphological classification of sessile serrated adenomas with dysplasia may represent an improvement on the current description as it correlates with the underlying mismatch repair protein status of the polyps and better highlights the range of morphologies seen by pathologists.

Epigenetic silencing of MLH1 in endometrial cancers is associated with larger tumor volume, increased rate of lymph node positivity and reduced recurrence-free survival.

OBJECTIVES: To determine the relationship between mismatch repair (MMR) classification and clinicopathologic features including tumor volume, and explore outcomes by MMR class in a contemporary cohort. METHODS: Single institution cohort evaluating MMR classification for endometrial cancers (EC). MMR immunohistochemistry (IHC)±microsatellite instability (MSI) testing and reflex MLH1 methylation testing was performed. Tumors with MMR abnormalities by IHC or MSI and MLH1 methylation were classified as epigenetic MMR deficiency while those without MLH1 methylation were classified as probable MMR mutations. Clinicopathologic characteristics were analyzed. RESULTS: 466 endometrial cancers were classified; 75% as MMR proficient, 20% epigenetic MMR defects, and 5% as probable MMR mutations. Epigenetic MMR defects were associated with advanced stage, higher grade, presence of lymphovascular space invasion, and older age. MMR class was significantly associated with tumor volume, an association not previously reported. The epigenetic MMR defect tumors median volume was 10,220mm3 compared to 3321mm3 and 2,846mm3, for MMR proficient and probable MMR mutations respectively (P<0.0001). Higher tumor volume was associated with lymph node involvement. Endometrioid EC cases with epigenetic MMR defects had significantly reduced recurrence-free survival (RFS). Among advanced stage (III/IV) endometrioid EC the epigenetic MMR defect group was more likely to recur compared to the MMR proficient group (47.7% vs 3.4%) despite receiving similar adjuvant therapy. In contrast, there was no difference in the number of early stage recurrences for the different MMR classes. CONCLUSIONS: MMR testing that includes MLH1 methylation analysis defines a subset of tumors that have worse prognostic features and reduced RFS.

Sessile Serrated Polyps are Precursors of Colon Carcinomas With Deficient DNA Mismatch Repair.

We investigated whether sessile serrated adenomas/polyps (SSA/Ps) are direct precursors of colorectal carcinomas. We identified colon carcinomas that arose from SSA/Ps among 2646 colorectal cancers included in the surgical pathology database at the Mayo Clinic (2006-2012). Molecular features of the serrated neoplasia pathway were analyzed in these tumors by immunohistochemical analyses of mutant BRAF (V600E) and MLH1 proteins. Among the 33 identified SSA/P-associated colonic adenocarcinomas (median patient age, 75 y), 24 developed in women (73%), 31 were located in the proximal colon (94%), and 23 (69%) were TNM stage I or II. Thirty-one of the tumors (94%) expressed mutant BRAF; of these, 26 also had loss of MLH1 (79%), indicating deficient DNA mismatch repair of sporadic origin. Twenty-two of the tumors (67%) were interval cancers that were more common in women and did not differ significantly in TNM stage, BRAF mutation, or loss of MLH1. By histopathology, SSA/Ps that were associated with colon carcinomas contained frequent dysplasia (48%). Most cancers that arose from SSA/Ps were located on the right side of the colon and had mutant BRAF and loss of MLH1. These findings indicate that SSA/Ps are precursors of most sporadic colon carcinomas with deficient DNA mismatch repair.

Analysis of Lynch Syndrome Mismatch Repair Genes in Women with Endometrial Cancer.

OBJECTIVE: Endometrial cancer is the second most frequent neoplasm in women with Lynch syndrome (LS). We sought to assess whether analyzing women with endometrial cancer would identify families with LS not identified with current clinical criteria. METHODS: We included women diagnosed with endometrial cancer younger than 50 years and also older if they had a family cancer history associated with LS. In blood samples obtained, we analyzed mutations in mismatch repair (MMR) genes, as well as protein expression by immunohistochemistry and microsatellite instability (MSI) in tumour tissue. RESULTS: A total of 103 patients were enrolled. We detected 14 pathogenic mutations and 4 genetic variants of unknown clinical significance in MMR genes. We found MSI in 41.66% of the women with a pathogenic mutation. In this group, 76.92% showed loss of at least one MMR protein. Women with mutations were younger at diagnosis, but all of them had a family history compatible with LS. CONCLUSIONS: Analysis of the MMR genes, in particular MSH6, seems to be appropriate in women with endometrial cancer and a family history of tumours associated with LS.

Lower prevalence of Lynch syndrome in colorectal cancer patients in a Japanese hospital-based population.

PURPOSE: The aim of this study was to investigate the prevalence of Lynch syndrome among Japanese patients with surgically resected colorectal cancer at a single institution. METHODS: Of 616 colorectal cancer patients who underwent surgical operation in our institution from January 2005 to August 2010, immunohistochemistry analyses for mismatch repair proteins (MLH1, MSH2, MSH6, and PMS2) and microsatellite instability (MSI) testing for surgically resected, formalin-fixed paraffin-embedded colorectal cancer specimens from 138 colorectal cancer patients under 60 years of age were undertaken. Hypermethylation of the MLH1 promoter and BRAF mutation were analyzed where necessary. RESULTS: Seven patients were identified as candidates for genetic testing by mismatch repair protein loss (n = 7) or MSI-H (n = 6). Methylation of MLH1 was detected in one case. Three patients were diagnosed with Lynch syndrome, comprising 2.2 % of the total colorectal cancer patients younger than 60 years of age. CONCLUSION: The prevalence of Lynch syndrome among hospital-based diagnosed cancer patients may therefore be lower than expected in Japan compared with Western populations.

Changing patterns of referrals and outcomes of genetic participation in gynaecological-oncology multidisciplinary care.

BACKGROUND: Genetic participation in gynaecological oncology multidisciplinary team meetings (MDT) may identify the sentinel cancer in women with hereditary breast-ovarian cancer syndrome or Lynch syndrome. AIMS: To identify the changing patterns of genetic referral from 2010 to 2014 and the outcomes of referrals through clinical MDT case review. MATERIALS AND METHODS: Medical records of cases of gynaecological cancer presented at the MDT meetings and genetics databases were reviewed to determine the frequency and outcomes of recommendations for genetic referral between 2010 and 2014. RESULTS: Four hundred and sixty-two women of 2523 cases reviewed were recommended for referral, increasing from 8% in 2010 to 25% in 2014. However, 167 of 462 patients (36%) had not registered with a Hereditary Cancer Clinic in NSW/ACT, including 11 women with high-grade serous ovarian cancer and seven women with abnormal MMR immunohistochemistry. Mutations were identified in 40 of 165 women (24%) undergoing breast cancer BRCA1/2 testing and in ten of 25 women (40%) who underwent MMR genetic testing. Eighty-one first- or second-degree relatives of these women have undergone predictive testing, identifying 48 mutation carriers and 33 non-carriers. CONCLUSION: Changing indications and increased participation by a genetic consultant in the weekly MDT meeting has led to increasing genetic referrals over the last five years. Follow up of referrals needs to be addressed. With decreasing costs of genetic testing and use of readily transportable DNA collected through saliva or mouth swabs, we propose that distance should not be a barrier to this model being extended to all centres providing care to gynaecological cancer patients.

[MICROSATELLITE INSTABILITY AND SURVIVAL IN PATIENTS WITH ENDOMETRIAL CANCER.]

Microsatellite-unstable genotype associated with deficiency mismach repaired enzymes leads to the accumulation of a series of mutations in the coding and regulatory regions of the genes having a role in carcinogenesis in endometrial cancer (ECs). The aim of this study was to investigate the correlation between the expression of four main mismach repaired enzyme (MLH-1, MSH-2, MSH-6 and PMS-2) with patients survival. ECs from 70 women (median of 63 years, range of 43-79 years) were assessed immunohistochemically for microsatellite instability (MSI). In our study we found that the presence of MSI, determined by the absence of immunohistochemically expression of at least one of the test four of the enzyme mismach repaired system is associated, not statistically significant, with longer survival (p = 0.558). In conclusion we may state that the immunohistochemical analysis who indicates MSI in biopsy tissue is a one step forward for the determination of survival and progression of endometrial carcinoma.

Immunohistochemical Screening of Upper Tract Urothelial Carcinomas for Lynch Syndrome Diagnostics: A Systematic Review.

OBJECTIVE: To review the effect of universal screening of newly diagnosed upper tract urothelial carcinomas (UTUC) for mismatch repair (MMR) protein loss to aid in Lynch syndrome diagnostics. MATERIALS AND METHODS: Studies were identified through PubMed on December 1, 2021. Eligibility criteria were universal immunohistochemical analyses for at least 2 MMR proteins in unselected, consecutively collected UTUC cohorts. Exclusion criteria included reviews, case-reports, non-English language, and non-humans. Risk of bias was assessed using a modified Newcastle-Ottawa scale. Meta-analyses were performed to compare the association between clinical criteria and Lynch syndrome diagnoses. RESULTS: From 12 included studies, 1628 surgically removed UTUC from 1626 patients were screened for MMR protein loss. In 11 studies, 140 of the 1559 patients had tumors with loss (9.0%) with 80.7% showing loss of MSH2, MSH6, or both. In 7 studies, genetic testing confirmed Lynch syndrome diagnosis for 20 of 970 patients (2.1%). In 8 studies, 31 patients were given a clinical Lynch syndrome diagnosis (2.6%). In total, 51 assumed or verified Lynch syndrome patients were identified among 1087 patients (4.7%). Meta-analyses of 3 studies showed significant association between previous cancer diagnosis and Lynch syndrome-associated UTUC (P = .038). CONCLUSION: Despite the few studies conducted and lack of genetic testing, current data suggests that universal screening for MMR protein loss in UTUC may result in Lynch syndrome diagnoses in 4.7%. However, for the screening to be effective for Lynch syndrome diagnostics, follow-up investigations, such as genetic testing for MMR variants, are needed.

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 compare IHC 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.

PD-L1, PARP1, and MMRs as potential therapeutic biomarkers for neuroendocrine cervical cancer.

OBJECTIVE: Neuroendocrine cervical cancer (NECC) is a rare cervical cancer with high aggressivity that causes poor prognosis even in the early stage. Given other neuroendocrine carcinomas and other types of cervical cancer have been proved to have expression of programmed cell death protein 1 ligand 1(PD-L1) and poly ADP-ribose polymerase-1(PARP1), we would measure and analyze these proteins in this invasive cancer. The purpose of this study is to investigate the application value of PD-1/PD-L1 and PARP1 inhibitors in NECC. METHODS: The NECC cases in our center with formalin-fixed paraffin-embedded tissue blocks were collected, and immunohistochemical (IHC) staining of PD-L1, PARP1, Mismatch repair proteins (MMRs), and P53 was performed. Chi-square test was used to analyze associations between various protein expressions. We analyzed the efficacy of immunotherapy in a recent patient with secondary recurrence after two courses of chemotherapy. RESULTS: After rigorous screening, 20 cases were finally included. Three cases did not undergo surgical treatment because of their advanced stage. Twelve (60%) developed distant metastases or relapsed within five years, and most of them within two years. The positive rate of PD-L1 and PARP1 were 70% and 75% respectively. Among all the cases, microsatellite instability (MSI) was seen in six cases (30%) and abnormal p53 expression was in 15 patients (75%). PD-L1 was associated with PARP1 expression in the MSI subgroup. The patient treated with chemotherapy + VEGF inhibitor (VEGFi) + programmed cell death protein 1(PD-1) inhibitor had an excellent improvement in clinical symptoms, tumor markers, and mass size. CONCLUSION: The IHC results of PD-L1, PARP1, and MMRs suggested that NECC was the target of immunotargeted therapy. Our case confirmed that immune checkpoint therapy was effective in patients with PD-L1 positive and MMRs loss. Considering the clinical practicability, more cases should be collected, and effective biomarkers still need to be further searched.