Colorectal cancer (CRC) is the third most common and second most deadly cancer worldwide. Despite advances in screening and treatment, CRC is heterogeneous and the response to therapy varies significantly, limiting personalized treatment options. Certain molecular biomarkers, including microsatellite instability (MSI), are critical in planning personalized treatment, although only a subset of patients may benefit. Currently, the primary methods for assessing MSI status include immunohistochemistry (IHC) for DNA mismatch repair proteins (MMRs), polymerase chain reaction (PCR)-based molecular testing, or next-generation sequencing (NGS). However, these techniques have limitations, are expensive and time-consuming, and often result in inter-method inconsistencies. Deficient mismatch repair (dMMR) or high microsatellite instability (MSI-H) are critical predictive biomarkers of response to immune checkpoint inhibitor (ICI) therapy and MSI testing is recommended to identify patients who may benefit. There is a pressing need for a more robust, reliable, and cost-effective approach that accurately assesses MSI status. Recent advances in computational pathology, in particular the development of technologies that digitally scan whole slide images (WSI) at high resolution, as well as new approaches to artificial intelligence (AI) in medicine, are increasingly gaining ground. This review aims to provide an overview of the latest findings on WSI and advances in AI methods for predicting MSI status, summarize their applications in CRC, and discuss their strengths and limitations in daily clinical practice.

Deficiency in DNA mismatch repair (dMMR) is a common pathway of carcinogenesis across different tumour types and confers a characteristic microsatellite instability-high (MSI-H) molecular phenotype. The prevalence of the MSI-H/dMMR phenotype is highest in endometrial and colorectal cancers, and this phenotype is associated with a distinct tumour biology, prognosis and responsiveness to various anticancer treatments. In a minority of patients, MSI-H/dMMR cancers result from an inherited pathogenic variant in the context of Lynch syndrome, which has important implications for familial genetic screening. Whether these hereditary cancers have a different biology and clinical behaviour to their sporadic counterparts remains uncertain. Interest in this tumour molecular subtype has increased following the discovery of the high sensitivity of metastatic MSI-H/dMMR cancers to immune-checkpoint inhibitors (ICIs) in a histology-agnostic manner, which reflects the genomic hypermutation resulting from dMMR that renders these tumours highly immunogenic and immune infiltrated. This vulnerability is now also being exploited in early stage disease settings. Despite this common biological foundation, different MSI-H/dMMR cancers have histotype-specific features that correspond to their particular cell or tissue of origin, which might be associated with differences in prognosis and sensitivity to ICIs. In this Review, we provide an overview of the epidemiology, biology, pathogenesis, clinical diagnosis and treatment of MSI-H/dMMR tumours as a histology-agnostic cancer phenomenon. We also highlight peculiarities associated with specific pathogenetic alterations and histologies of MSI-H/dMMR tumours.

Effective biomarkers are necessary for early diagnosis, prognosis, and therapy monitoring of colorectal cancer (CRC), a disease that continues to be a major worldwide health problem. Due to a potential connection to colorectal cancer, serum gamma-glutamyl transferase (GGT), an important enzyme in metabolism of glutathione and cellular stress response, has drawn attention. GGT is an essential component of the antioxidant system that protects against oxidative stress. It is mostly found in organs such as the liver, kidneys, and biliary tract. Numerous health problems, such as metabolic disorders, liver illnesses, and several types of cancer, are linked to elevated blood GGT levels. This review aims to clarify the function of serum GGT in colorectal cancer by examining clinical research conducted over the past 20 years. A comprehensive analysis of pertinent literature identifies associations between high blood GGT levels and carcinoma of the colon risk, prognosis, and diagnostic potential. Increased GGT and a higher risk of colorectal cancer are positively correlated, according to epidemiological data consistently. The predictive capacity of GGT for colorectal adenomas underscores its use in early identification and preventive approaches. Additional clinical evidence indicates that higher GGT levels in CRC patients are associated with poorer outcomes, such as invasion of lymph nodes, advanced tumour stages, and decreased overall survival. Furthermore, changes in GGT levels after therapy offer information about patient survival and treatment effectiveness, highlighting its importance in therapy monitoring. In summary, this review underscores the multifaceted role of serum GGT in CRC, offering insights into its value as a biomarker for risk assessment, prognosis, and therapeutic monitoring, while emphasizing the need for further research to validate its clinical utility.

Microsatellite instability (MSI) and deficiency in the human mismatch repair (MMR) system are critical drivers of genomic instability in various cancers. Tumors exhibiting MSI and MMR deficiency (dMMR) have prognostic implications and are associated with differential responses to immune checkpoint inhibitors. Given their key roles in tumorigenesis, investigating MMR protein expression and MSI in urothelial cancer of the bladder is essential to improve therapeutic strategies and deepen understanding of its molecular features. This study aimed to assess MMR protein expression and MSI in primary urothelial carcinoma of the bladder and to evaluate their associations with clinicopathological characteristics.

A total of 49 primary urothelial carcinomas were analyzed for MMR expression using immunohistochemistry, and dMMR tumors underwent further analysis for MSI status using the markers of the Bethesda panel (BAT25, BAT26, D2S123, D5S346, and D17S250). The MMR expression and MSI findings were associated with clinicopathological parameters.

dMMR was identified in two high-grade urothelial carcinomas (4.1%), while the remaining cases demonstrated proficient MMR. Both dMMR tumors showed impaired immunoreactivity, with one tumor displaying a simultaneous loss of the MLH1/PMS2 heterodimer and the other showing isolated MSH6 loss. MSI analysis revealed instability in BAT26 in the MLH1/PMS2-deficient tumor and at D17S250 in the MSH6-deficient tumor. Both tumors exhibited low-level MSI (MSI-L). No relevant associations were found between MMR/MSI status and clinicopathological features (p > 0.05).

The identification of MSI-L and MMR deficiency in only two samples underscores the rarity of MSI in urothelial carcinoma among Tunisian patients. These findings emphasize the need for larger, multi-center studies to elucidate the MSI/dMMR molecular and clinical implications in bladder carcinoma.

Lynch syndrome (LS) is a hereditary cancer predisposition syndrome caused by germline pathogenic variants of DNA mismatch repair (MMR) genes. To diagnose LS, the microsatellite instability (MSI) test or immunohistochemistry of MMR enzymes is used as a conventional clinical screening method for all patients with colorectal and endometrial cancers. Recently, patients with advanced-stage cancers have undergone comprehensive genomic profiling (CGP), which is useful not only for the detection of molecularly targeted personalized therapies, but also for the screening of hereditary cancer syndromes by determining presumed germline pathogenic variants (PGPVs). Between January 2020 and April 2024, 1583 patients underwent CGP at our institute. PGPVs in MMR genes were detected in 19 patients. Although one patient died prior to the disclosure of the results and eight patients declined confirmatory genetic testing, the remaining ten patients underwent confirmatory genetic tests, of whom six were found to have a hereditary origin. Two additional patients were diagnosed with LS using tumor-normal paired CGP. Eventually, a total of eight patients were diagnosed with LS. Herein, we describe two patients with microsatellite-stable cancer who could not be diagnosed using conventional clinical screening or MSI testing. Furthermore, we showed that pathogenic variants of MMR genes do not always correlate with high MSI prediction scores in several cancer types in The Cancer Genome Atlas (TCGA) dataset analysis. These findings highlight the usefulness of CGP as a screening tool to identify individuals with possible LS, especially when conventional criteria and MSI/MMR testing fail.

Contemporary diagnostic and therapeutic strategies for many solid tumors rely on understanding the Mismatch Repair (MMR) system, a fundamental DNA repair mechanism responsible for correcting errors introduced during DNA replication. Pathology reports written for tumors excised in surgery, often indicate the expression status of MMR proteins. This is of significant clinical value, as loss of MMR protein expression is associated with the accumulation of DNA replication errors. The MMR system recognizes and replaces mismatched nucleotides, particularly in microsatellite regions. These are short, repetitive non-coding DNA sequences prone to replication errors. When MMR proteins are inactivated by genetic or epigenetic alterations, MMR deficiency (dMMR) occurs, preventing repair and leading to microsatellite instability (MSI). MSI is a hallmark of Lynch syndrome, which is commonly associated with colorectal cancer (CRC) and endometrial cancer. This work highlights the clinical utility of MMR protein and MSI status as molecular signatures and discusses diagnostic, prognostic, and therapeutic implications. Understanding these molecular changes supports clinicians in making informed therapeutic decisions and may improve patient outcomes by providing personalized treatments to fit individual tumor profiles.

The integrity of the genome is maintained by mismatch repair (MMR) proteins that recognize and repair base mismatches and insertion/deletion errors generated during DNA replication and recombination. A defective MMR system results in genome-wide instability and the progressive accumulation of mutations. Tumors exhibiting deficient MMR (dMMR) and/or high levels of microsatellite instability (termed "microsatellite instability high", or MSI-H) have been shown to possess fundamental differences in clinical, pathological, and molecular characteristics, distinguishing them from their "microsatellite stable" (MSS) counterparts. Molecularly, they are defined by a high mutational burden, genetic instability, and a distinctive immune profile. Their distinct genetic and immunological profiles have made dMMR/MSI-H tumors particularly amenable to treatment with immune checkpoint inhibitors (ICIs). The ongoing development of biomarker-driven therapies and the evaluation of novel combinations of immune-based therapies, with or without the use of conventional cytotoxic treatment regimens, continue to refine treatment strategies with the goals of maximizing therapeutic efficacy and survival outcomes in this distinct patient population. Moreover, the resultant knowledge of the mechanisms by which these features are suspected to render these tumors more responsive, overall, to immunotherapy may provide information regarding the potential optimization of this therapeutic approach in tumors with proficient MMR (pMMR)/MSS tumors.

To identify exonic markers that could improve analytic performance characteristics of next-generation sequencing (NGS) in detecting mismatch repair deficiency (dMMR) using colorectal cancer (CRC) as a model.

Coding sequences of a target NGS panel (~1.13 megabase) were compared between dMMR CRC and mismatch repair-proficient (pMMR) CRC in a training cohort (41 dMMR CRCs and 213 pMMR CRCs) and a validation cohort (33 dMMR CRCs and 307 pMMR CRCs) with documented mismatch repair status by immunohistochemical and/or microsatellite instability assays.

The dMMR CRC cases showed significantly higher insertion/deletion (indel) mutations within exonic homopolymers (homo-indels), occurring predominantly within longer repeats of 5 to 10 nucleotides (92%, P < .0001), rather than shorter repeats of 2 to 4 nucleotides seen in pMMR CRC (62%). Homo-indels in dMMR CRC were not random. Hotspot loci were consistent between the training and validation cohorts. The dMMR defined by indels within homopolymers of 5 or more nucleotides, homopolymers of 7 or more nucleotides, or a panel of hotspots all showed 100% sensitivity and specificity with a range of cutoffs.

We propose that this approach allows one to identify highly sensitive and specific markers for detecting dMMR CRC by NGS alone. Further studies are warranted to test whether these markers are applicable to non-CRC neoplasms.

Pancreatic cancer is a highly aggressive and lethal disease, characterized by a limited response to chemotherapy and overall poor prognosis. Pancreatic cancers with a distinct mismatch repair deficiency, although relatively rare, have been shown to be associated with markedly better outcomes in comparison. Furthermore, whereas pancreatic cancers are generally unresponsive to current immunotherapy, this specific group of tumors has been shown to have a notable susceptibility to immune checkpoint inhibitors.

In this review, we aim to summarize the relevant literature regarding mismatch-repair associated pancreatic cancers, the impacted biological mechanisms, and the resulting vulnerabilities for potential opportunistic immunotherapeutic treatment approaches. We will also review the current clinical studies assessing survival outcomes of mismatch repair deficient pancreatic cancers and ongoing clinical trials in this emerging field.

Patients with dMMR/MSI-H pancreatic cancers harbor a distinct phenotype that has increased immune activation, greater responsiveness to immune checkpoint inhibitor therapy and better overall survival when compared to other pancreatic cancers. Although this molecular subtype makes up a small minority of cases, emerging data suggest immunotherapy may offer benefit to these patients.

Hereditary colorectal cancer (CRC) syndromes account for up to 5% of CRC. Patients have an increased risk of CRC and extracolonic cancers, both of which develop at an early age. The main polyposis syndromes include familial adenomatous polyposis, MYH-associated polyposis, Peutz-Jeghers syndrome, juvenile polyposis syndrome, and PTEN hamartoma syndrome. The non-polyposis syndromes include Lynch syndrome and familial colorectal cancer type X. Each of the syndromes have distinct but sometimes overlapping phenotypes. Clinical evaluation and ultimately the underlying germline genetic pathogenic variants define the syndromes. Each syndrome has polyp, CRC, and extracolonic risks and management is based on early and timely surveillance with therapeutic and often extended prophylactic surgery. Surgical intervention strategies are individualized, considering not only the earlier onset of malignancies and heightened risks for metachronous cancers but also the patient's needs and quality of life. This article reviews the different diagnostic approaches to hereditary CRC and highlights subsequent disease-specific management and surgical decision-making strategies.

Claudin 18.2 is an emerging biomarker for claudin 18.2-targeted therapy. We investigated claudin 18.2 expression in diverse tumor types.

We retrospectively analyzed 67 gastric tumors (61 surgically resected and six biopsy specimens) and 73 other tumor types (69 resected and four biopsy specimens), including those from the pancreas, hepatobiliary system, lung, ovary, uterine cervix, and others. Claudin 18.2 expression and positivity (≥75% of tumor cells showing moderate to strong membranous staining) were assessed using claudin 18 immunostaining (clone 43-14A).

Claudin 18.2 positivity was found in 47.8% (32/67) of gastric tumor samples. Epstein-Barr virus-associated gastric cancer showed a higher frequency of positivity (6/7, 85.7%), although not statistically significantly (p=0.216). Among gastric tumors from patients with lymph node or distant metastasis (n=20), four (20.0%) exhibited discrepancies in claudin 18.2 positivity between the primary and its metastasis. In other tumor types, claudin 18.2 positivity was more frequent in those with gastric epithelium-like differentiation, including pancreatic tumors (2/9, 22.2%), hepatobiliary carcinoma (2/8, 25.0%), invasive mucinous lung adenocarcinoma (4/5, 80.0%), and mucinous ovarian tumor (5/5, 100.0%) than in those with other histology (p<0.001). Interestingly, pancreatic tumors, potential candidates for claudin 18.2-targeted therapy, often exhibited reduced or lack of claudin 18.2 expression in the invasive component.

Overall, claudin 18.2 positivity occurred primarily in a significant proportion of gastric tumors and other tumors with gastric epithelium-like differentiation. Evaluating claudin 18.2 expression in all such tumors can benefit patients by guiding targeted therapy. Additionally, claudin 18.2 immunostaining serves as a lineage marker for gastric origin or gastric-like differentiation.

Lynch syndrome (LS) increases the risk of various cancers, including colorectal cancer, endometrial cancer and gastric cancer (GC). The incidence of LS among microsatellite instability-high (MSI-H) GC and their association in South Korea remains underexplored. This study investigates LS-associated pathogenic germline variants in MSI-H GC patients using whole-exome sequencing (WES) on normal tissues.

This retrospective study included patients who underwent gastrectomy for GC at Soonchunhyang University Bucheon and Cheonan Hospitals from January 2011 to October 2023. Among 1,537 patients screened for MSI status, 127 (8.3%) were identified as MSI-H. WES was performed on normal tissues from 123 patients. Pathogenic/likely pathogenic (P/LP) variants in mismatch repair (MMR) genes were identified using in silico models and protein loss assessments in corresponding tumor tissues.

Of the 127 MSI-H GC cases, characteristics aligned with typical MSI-H GC. The average age was 70.02 years, with 98 (77.2%) located in the lower body and 81 (63.8%) of the intestinal type. All five MSI markers were positive in 46.5% of cases, whereas four markers were positive in 27.6%. Of the MSI-H GCs, 10 LS candidates were identified. Three patients had known P/LP variants [MLH1 (c.1758dup), MSH6 (c.3261dup), MSH2 (c.1241T>C)]. Seven patients had variants of unknown significance (VUS) in MMR genes. Six (4.9%) patients were identified as having LS or possible LS, including one patient with the MLH1 (c.1153C>T) variant previously classified as VUS but now considered LS-associated.

This large-scale screening for LS in MSI-H GC patients using retrospective samples confirmed the lower incidence of LS than those of colorectal or endometrial cancer and GC patients in Western countries, emphasizing the need for clinical consideration in managing MSI-H GC patients.

Background and Objectives: Lynch syndrome (LS), an autosomal dominant condition arising from germline mutations in mismatch repair (MMR) genes, is a major cause of hereditary early-onset colorectal cancer (CRC). Although patients diagnosed before age 50 represent a critical subgroup where Lynch syndrome might be more prevalent, data on the precise frequency, clinical outcomes, and molecular correlates remain heterogeneous across studies. This systematic review was conducted to (1) estimate the prevalence of MMR deficiency (dMMR) and confirmed LS in patients diagnosed with CRC before the age of 50, and (2) examine immunohistochemistry (IHC) mismatch repair testing patterns and associated molecular findings (BRAF mutations, MLH1 promoter hypermethylation, somatic MMR gene alterations). Methods: Following a predefined search strategy in PubMed, Scopus, and Web of Science, five relevant studies were identified (n = 5). Each study comprised patients younger than 50 who underwent IHC-based tumor screening. Data extraction covered demographic details, number of patients tested, proportion with abnormal IHC, frequency of somatic or germline MMR gene mutations, and method of classification into sporadic dMMR vs. LS. Quality assessment was performed using recommended scales for observational studies. Results: Among 5 studies totaling 960 early-onset CRC patients, the frequency of dMMR CRC ranged from 8.4% to 19.1%. The confirmed prevalence of LS among all young-onset CRC was between 5.0% and 5.9% in three studies but reached 8.9% in another and 5.1% in yet another. Across all studies, the presence of right-sided tumors and histopathological features such as tumor-infiltrating lymphocytes were more common in dMMR cancers. Incorporation of MLH1-promoter hypermethylation and/or BRAF V600E mutation testing aided discrimination of sporadic dMMR CRC from germline LS cases. Conclusions: The prevalence of LS in CRC patients younger than 50 is clinically significant, at approximately 5-9%. Routine IHC-based MMR screening is both feasible and effective for detecting LS in early-onset CRC. Further research is needed to standardize universal testing protocols, delineate the role of additional molecular assays, and ensure comprehensive genetic counseling for at-risk individuals.

Approximately 10% of colorectal cancer (CRC) cases occur in the context of hereditary cancer-predisposing conditions caused by germline pathogenic variants (PVs) in cancer predisposition genes, with Lynch syndrome and familial adenomatous polyposis at the top of the list. Although the identification of hereditary CRC has traditionally relied on clinical characteristics, including familial accumulation, multiple and early onset of CRC and other related cancers, and the presence of gastrointestinal polyposis, more comprehensive approaches, such as universal tumor screening and universal germline testing, have recently been employed. From a technical standpoint, next-generation sequencing has enabled genome-wide analysis of genetic alterations in germline and somatic settings. Taking advantage of this technology, germline multigene panel testing has been utilized in genetic testing, which leads to the identification of PVs, not only in well-known hereditary CRC genes but also in rare causal genes, moderate-risk genes, and high-risk genes previously not linked to CRC predisposition. In addition, comprehensive genomic profiling and companion diagnostics for solid tumors occasionally yield unexpected hereditary CRC diagnoses. Thus, more hereditary CRCs have been identified not based on clinical phenotypes but rather by comprehensive approaches or as secondary findings of treatment drug testing. In this review, we discuss the impact of recent advances in genomic medicine on the clinical aspects of hereditary CRC, which has promoted an understanding of the entire landscape of genetic predisposition to CRC.

Lynch-like syndrome (LLS) presents very similar clinicopathological characteristics to Lynch syndrome (LS) but the mechanism for cancer predisposition remains unknown. The present study aims to investigate the causal mechanism of LLS by a comprehensive genetic and epigenetic approach. Thirty-two LLS and 34 LS patients with colorectal cancer (CRC) fitting the Amsterdam and Bethesda criteria were included, along with 29 CRC sporadic patients, and analyzed for the presence of pathogenic variants in 94 genes associated with hereditary tumors. The cohorts were also characterized for the methylation profile and examined through a sample group analysis and a Stochastic Epigenetic Mutations (SEMs) analysis in comparison with 29 age-matched healthy controls. The multigene panel analysis revealed the presence of pathogenic variants in non-mismatch repair (MMR) genes and three variants classified as pathogenic/likely pathogenic possibly predisposing to LLS. The epigenetic analysis showed epivariations targeting genes associated with LS or DNA repair, most of them associated with the Fanconi Anemia pathway, which could explain the susceptibility to cancer. Our results highlight the need for using extended genetic and epigenetic analyses to understand the causal mechanism of LLS.

Deficient mismatch repair (dMMR) and/or microsatellite instability (MSI) colorectal cancer (CRC) is highly sensitive to immune checkpoint inhibitors (ICI). It is thus becoming increasingly relevant to monitor circulating tumor DNA (ctDNA) and to determine the MSI status (ctDNA-MSI) in CRC. So far, few studies have explored this, even though it could be particularly relevant in evaluating treatment efficacy in patients with dMMR and/or MSI CRC. The ctDNA DIgestive cancers MSI study (ADI-MSI) aims to assess the value of ctDNA-MSI as a predictor of ICI efficacy. Blood samples were collected prospectively in a single-center cohort to analyze circulating cell-free DNA (cfDNA) and ctDNA-MSI before the start of and during treatment. ctDNA-MSI was measured using digital droplet PCR with the 5 microsatellite markers of the Pentaplex panel (Promega Corporation). The primary endpoint was to evaluate ctDNA-MSI levels as a predictor of progression-free survival (PFS). We included 54 patients with dMMR and/or MSI CRC, most of whom had metastatic disease (77.8%) treated in the first (25.9%) or second line (42.6%) with ICI. High-baseline cfDNA and ctDNA-MSI were associated with worse PFS and overall survival. ctDNA-MSI kinetics, but not cfDNA kinetics, was associated with treatment response (P = .006), PFS (P = .03), and overall survival (P = .04). ctDNA-MSI kinetics divided into 3 groups (increase, decrease, and negative) correlated strongly with PFS (PFS at 24 months was 0%, 53.0%, and 77.0%, respectively; P < .001) and remained significant in multivariate analysis (hazard ratio = 7.93; 95% CI, 2.23-28.21; P = .005). As there is no strong predictor of ICI efficacy in patients with dMMR and/or MSI CRC, these results suggest that ctDNA-MSI could help physicians in treatment decision-making in the future.

Hereditary cancer syndromes account for 6-10% of all colorectal cancer (CRC) cases and 20% of early-onset CRC. Identifying novel pathogenic germline variants can impact genetic testing, counseling, and surveillance. This study aimed to determine the prevalence of germline variants associated with hereditary CRC in the Iranian population.

Whole exome sequencing (WES) was conducted on DNA from 101 patients in the Iranian Hereditary Colorectal Cancer Registry (IHCCR). The cohort included 63 high-risk Lynch Syndrome (LS) patients and 38 colorectal polyposis patients. Germline variants and phenotype spectrum were assessed. Relatives of individuals with the mutations received counseling and cascade testing. Gene ontology and protein-protein interaction (PPI) analyses were conducted to elucidate gene roles on protein function.

Pathogenic/likely pathogenic (P/LP) variants were identified in Lynch-related genes in 36.51% of patients. P/LP variants in non-Lynch genes (ATM, FH (mono-allelic), MSH3, PMS1, and TP53) were identified in 26.98% of patients. Among polyposis patients, 50% had P/LP variants in the APC gene, and 15.79% had P/LP variants in the MUTYH gene. Additionally, 7.89% carried P/LP variants in non-FAP/MAP genes (BLM, BRCA2, and PTEN). MLH1 variants were most common in exons 10 and 18, MSH2 in exon 12, and APC gene in exon 16. Cascade testing identified 50% of the tested relatives (40/80). Topology analysis of the protein-protein interaction networks in high-risk LS cases highlighted stronger connections among nodes for genes such as TP53, ATM, POLD1, CDH1, MUTYH, WRN, NOTCH1, SMAD4, ERCC4, ERCC1, and MSH3. These genes were associated with high penetrance in CRC. The protein-protein interaction analyses of polyposis patients indicated that genes like POLE, MSH6, MSH2, BRCA2, BRCA1, MLH1, TOPBP1, BLM, RAD50, MUTYH, MSH3, MLH3, PTEN, BRIP1, and POLK had a higher degree value and were also associated with high penetrance. Gene ontology and protein-protein interaction (PPI) analysis showed that some of the top-scoring non-Lynch genes were TP53, ATM, POLD1, CDH1, MUTYH, WRN, NOTCH1, SMAD4, ERCC4, ERCC1, and MSH3.

The study identified crucial germline variants for hereditary polyposis and non-polyposis CRC pathogenesis in the Iranian population. A selective strategy and cascade genetic testing are recommended for the diagnosis of hereditary colorectal cancer syndromes.

MSI is a crucial biomarker for selecting CRC patients for immunotherapy. Here, we analyze the first results from the observational prospective trial BLOOMSI (NCT06414304), which investigated the impact of MSI/dMMR testing methods and baseline tumor heterogeneity on treatment outcomes. Thirty MSI/dMMR+ CRC patients, who were candidates for immunotherapy, were enrolled. Depending on the local test used for MSI/dMMR, central PCR/IHC was performed. Baseline FFPE and liquid biopsy (LB) were analyzed with NGS. ORR (objective response rate) in the ITT population was 50% (95% CI, 31.3-68.7%). Concordance between local/central dMMR/MSI testing was 81%, and the concordance of IHC, PCR, NGS/FFPE, and NGS/LB was 68.4%. The ORR was similar for IHC+, PCR+, NGS/FFPE+, and NGS/LB+ patients (55.6%, 55.6%, 55%, and 57.9%, respectively). The ORR among patients with discordant IHC/PCR results was 0%, and the ORR among patients with NGS/LB-ORR was 25% (2/8 CR). Next, we performed quantitative MSI analysis, reflecting the clonality of MSI+ tumor cells. Multivariate analysis identified MSI clonality in FFPE (HR 0.63, 95% CI, 0.39-0.99, p = 0.0487) and LB (HR 3.05, 95% CI, 2.01-4.65, p < 0.00001) as independent predictors of progression. The ORR in patients with high clonality (≥7%, n = 4, NGS/LB) was 25%. We describe baseline methodological predictors of non-response to immunotherapy and propose a strategy for selecting potential non-responders. These findings warrant further investigation.

Lynch syndrome (LS)-also known as Hereditary Non-Polyposis Colorectal Cancer (HNPCC)-is caused by pathogenic germline mutations in DNA mismatch repair (MMR) genes such as MLH1, MSH2, MSH6, and PMS2. Although it accounts for only 1-5% of all colorectal cancers (CRCs), LS presents with a particularly high lifetime cancer risk and often occurs at younger ages. Identifying LS in patients under 60 years old is crucial for targeted surveillance and early interventions. Variations in clinical presentation and prognosis may exist based on the specific gene mutated, yet these patterns are not fully elucidated. This review aims to synthesize data on clinical outcomes among LS patients under 60, with an emphasis on how different MMR gene mutation patterns might influence prognosis, survival, and treatment decisions. Five population-based studies examining CRC patients younger than 60 years were included according to predefined eligibility criteria. Two independent reviewers screened and extracted data focusing on MMR deficiency detection methods (microsatellite instability [MSI] and/or immunohistochemistry [IHC]), rates of confirmed germline mutations, frequency of BRAF testing, and clinical endpoints such as stage distribution, survival outcomes, and recurrence. Risk of bias was assessed using standardized tools appropriate to each study design. The synthesis focused on comparing outcomes among individuals with MLH1, MSH2, MSH6, and PMS2 mutations, as well as delineating the proportion of patients with sporadic MSI under 60 years of age. Across the five studies, MSI positivity in CRC patients under 60 years ranged from 7.5% to 13%. The frequency of confirmed germline MMR mutations varied between 0.8% and 5.2% in specific cohorts, aligning with LS prevalence estimates of 1-5%. Different mutation patterns correlated with some variation in clinical presentation. Cases with MSH2 and MLH1 mutations more frequently exhibited synchronous or metachronous tumors, while MSH6 and PMS2 mutations displayed more heterogeneous IHC patterns. Where survival data were provided, LS patients under 60 years had better overall survival compared to MMR-proficient individuals, though some studies also noted a potential lack of benefit from standard 5-fluorouracil adjuvant therapy in MMR-deficient tumors. Screening by MSI or by IHC-supplemented with BRAF mutation testing to exclude sporadic MSI-facilitates early detection of LS in CRC patients under 60 and highlights notable differences between mutation types. Although overall outcomes for LS patients can be favorable, especially for stage II disease, the precise impact of each specific mutated gene on clinical course remains heterogeneous. Future large-scale prospective studies are needed to clarify optimal screening protocols and individualized treatment strategies for LS patients under 60.

In Japan, immunohistochemistry for mismatch repair (MMR) proteins targeted at stage II and III colorectal cancers (CRCs) has been covered by national insurance since October, 2022. This study aimed to clarify the long-term outcomes of patients with stage II and III CRCs receiving postoperative adjuvant chemotherapy based on their MMR status.

The outcomes of 640 patients who underwent radical surgery for stage II and III CRCs were analyzed retrospectively.

Deficient MMR (dMMR) was diagnosed in 41 (13.3%) patients with stage II and 28 (9.1%) patients with stage III CRC. The overall survival and recurrence rates were not significantly different between the patients with stage II and those with stage III CRC. The risk factors for recurrence among those with stage II CRC were tumors on the left side, T4 disease, and the presence of BRAF wild type. The recurrence rates were lower in the stage II CRC patients with sporadic dMMR than in those with suspected Lynch syndrome (LS). The first site of recurrence was more frequently the peritoneum or distant lymph node in patients with dMMR.

Stage II CRC patients with sporadic dMMR were found to have a very good prognosis. On the other hand, peritoneal dissemination or distant lymph node metastasis tended to develop in patients with dMMR.

Background: Hereditary colorectal cancer syndromes, including familial adenomatous polyposis (FAP), Lynch syndrome (LS), and Peutz-Jeghers syndrome (PJS), are associated with an increased risk of small bowel cancer (SBC). Due to the low incidence and non-specific presentation of SBC, effective surveillance strategies are essential for early detection and management. This review aims to evaluate and compare current endoscopic techniques for small bowel surveillance in these patients. Methods: A comprehensive review was conducted using peer-reviewed studies sourced from PubMed. Various endoscopic modalities, including capsule endoscopy (CE), device-assisted enteroscopy (DAE), and intraoperative enteroscopy (IOE), were assessed for their diagnostic yield, safety, and clinical utility. Surveillance recommendations of the different syndromes were also examined. Results: CE offers high sensitivity but lacks histological sampling capability. DAE, including double-balloon enteroscopy (DBE) and single-balloon enteroscopy (SBE), enables direct visualization, biopsy, and therapeutic interventions, albeit with greater procedural complexity. In FAP, duodenal surveillance follows the Spigelman classification to stratify cancer risk, while jejunal and ileal polyps remain less studied. LS patients have an increased SBC risk, warranting tailored endoscopic approaches. In PJS, surveillance aims to mitigate intussusception risks and allow early malignancy detection. Conclusions: Optimized surveillance strategies in hereditary colorectal cancer syndromes require a multimodal approach, integrating advanced endoscopic techniques with genetic risk stratification. Centralized care in tertiary centers improves outcomes by ensuring standardized surveillance protocols and enhancing early cancer detection. Artificial intelligence (AI) applied to CE and DAE is shaping promising prospects for the future surveillance of small bowel polyps by enhancing diagnostic accuracy and reducing the duration of the diagnostic process. Further research should investigate AI-assisted imaging and molecular biomarkers to optimize screening strategies.

Approximately 30% of endometrial cancers are associated with microsatellite instability (MSI) caused by deficiencies in the DNA mismatch repair (MMR) genes (dMMR). MMR testing by immunohistochemistry for MMR proteins and MSI testing by polymerase chain reaction (PCR) are routinely utilized to screen patients with colorectal cancer and endometrial cancer for Lynch syndrome and, more recently, to identify patients eligible for immunotherapy. The Biocartis Idylla™ MSI assay is a fully automated, cartridge-based real-time PCR assay. The assay uses as little as one formalin-fixed paraffin-embedded (FFPE) tumor section and is designed to detect seven novel MSI biomarkers consisting of short homopolymers located in ACVR2A, BTBD7, DIDO1, MRE11, RYR3, SEC31A and SULF2 genes. Mutation in two of these markers is considered MSI-H. FFPE of 35 ECs (25 dMMR and 10 microsatellite stable (MSS)) were used in this study. When tumor content was ≤20% on a slide, macrodissection was performed. The overall percent agreement with MMR IHC was 97% (31/32) with sensitivity = 96% and specificity = 100%. Pre-analytic evaluation of the manufacturer's recommended 20% tumor content cut-off is essential to ensure valid results. The Idylla MSI assay offers several advantages over other PCR-based assays including minimal hands-on time, rapid turn-around-time, no requirement for a paired normal sample and the use of FFPE directly without an extraction step.

Understanding the genetic heterogeneity of Lynch syndrome (LS) cancers has led to significant scientific advancements. However, these findings are widely dispersed across various resources, making it difficult for clinicians and researchers to stay informed. Furthermore, the uneven quality of studies and the lack of effective translation of knowledge into clinical practice create challenges in delivering optimal patient care. To address these issues, we developed and launched the Precision Lynch Syndrome Knowledge Base (PLSKB), a specialized, interactive web-based platform that consolidates comprehensive information on LS.

To create the PLSKB, we conducted an extensive literature review and gathered data from reliable sources. Through an extensive literature review and survey of other reliable sources, we have extracted prominent and relevant content with a high level of accuracy, transparency, and detailed provenance. To enhance usability, we implemented an evidence-leveling framework, categorizing studies on the basis of the type of research, reliability, and applicability to clinical care. The platform is designed to be dynamic, with updates performed monthly to incorporate the latest research.

The PLSKB integrates a broad spectrum of data related to LS, including biomarkers, cancer types, screening and prevention strategies, diagnostic methods, and therapeutics options. This centralized resource is intended to support clinicians and researchers in making evidence-based decisions throughout surveillance and care processes. Its interactive design and frequent updates ensure that users have access to the most current and relevant findings.

The PLSKB bridges the gap between research and clinical practice by offering a reliable, up-to-date repository of evidence-based information. This tool empowers clinicians and researchers to deliver precision care and advance research for LS and related conditions, ultimately improving patient outcomes.

In Latin America, genetic testing for Lynch syndrome (LS) has been partially implemented. Traditionally, LS diagnosis relied on the Amsterdam criteria and Bethesda guidelines, collectively known as traditional screening (TS). However, TS may miss up to 68% of LS cases. To improve detection rates, universal tumor screening (UTS) has been introduced. UTS involves screening all newly diagnosed patients with colorectal cancer for molecular markers to more effectively identify LS cases.

Clinical and molecular data on 1684 patients with colorectal cancer, collected between 1999 and 2020, were provided by 24 Latin American genetic cancer registries and centers. Germline genetic testing was not consistently performed across all cases.

LS screening strategies were available for 72% (1209/1684) of cases, with germline testing conducted in one-quarter (304/1209) of these. Most cases (78%; n = 943) underwent UTS, primarily in Argentina, Chile, and Uruguay, whereas 22% (266/1209) were screened through TS. UTS identified deficient mismatch repair tumors in 29% (272/943) of cases. The rate of LS confirmed by sequencing was higher with UTS (53.3%; 65/122) compared with TS (47.8%; 87/182), although the difference was not statistically significant (P = .175).

UTS is widely implemented in Latin America; however, the low detection rate of LS demonstrated in this study raises concerns about the routine use of germline genetic testing in our region. Our study provides real-world outcomes that highlight disparities in screening uptake and counseling referrals, illustrating the challenges that Latin American countries face in hereditary cancer syndrome screening. These results contribute to the rationale for designing effective screening strategies for LS, which may also be applicable to other hereditary cancer syndromes, ultimately.

Green tea consumption has been implicated in various biological activities, with particular emphasis on its anticancer properties. The antineoplastic effects of green tea are primarily attributed to its rich polyphenol content, among which, epigallocatechin-3-gallate (EGCG) is recognized as the most bioactive and potent catechin, responsible for the majority of its anticancer activity. This review provides a detailed examination of the in vitro and in vivo effects of green tea components, focusing on their potential therapeutic implications in colorectal cancer. The molecular mechanisms of action and bioactive constituents of green tea are systematically discussed, alongside an evaluation of experimental evidence supporting their efficacy. Furthermore, insights into the relationship between green tea dietary intake and colorectal cancer risk are analyzed, with a particular emphasis on clinical data and findings from meta-analyses involving patients diagnosed with colon cancer. The aggregated evidence underscores the necessity for well-designed randomized controlled trials and longitudinal cohort studies to substantiate the role of green tea as a chemopreventive agent. Additionally, future investigations should prioritize determining the optimal dosages, the appropriate durations of consumption, and the potential modulatory effects of dietary or lifestyle factors on green tea's anticancer efficacy.

Sarcomas do not belong to the Lynch Syndrome (LS)-tumour spectrum. A growing body literature has reported sarcomas in patients with LS. Clinical and tumour characteristics of these patients remain unknown.

We set up the first national retrospective study, SarcLynch, describing the pathological and clinical characteristics of sarcomas developed in patients with LS. Patients were identified from two national networks and included from 23 centres in France.

Eighty-one patients participated in the SarcLynch study. Sixty-seven (83 %) tumours were soft-tissue sarcomas (STS) and 14 (17 %) bone sarcomas. Among STS, 59 (88 %) showed a pleomorphic component, with undifferentiated pleomorphic sarcoma (UPS) (36 %) and pleomorphic rhabdomyosarcoma (pRMS) (21 %) being the most represented subtypes. Sarcoma was the first neoplastic event in 32 patients (40 %). Thirty-two patients (40 %) were carriers of MSH2 germline pathogenic variants. Among patients who underwent an assessment of deficient mismatch repair (dMMR) by immunohistochemistry and/or molecular biology status, 75 % were dMMR by immunohistochemistry and 45 % were microsatellite instability high (MSI-H). Eight patients received immune checkpoint inhibitors and 4 (50 %) exhibited an objective response with 3 complete radiological response including 1 patient with pathological complete response. Duration of response ranged from 6 to 20 months.

SarcLynch, the largest multicentric series describing sarcomas developed in patients with LS, revealed an enrichment in patients with pleomorphic sarcomas - especially UPS and pRMS. This finding strongly supports screening for MMR status evaluation in these rare histotypes both for oncogenetic screening and therapeutic interest. Considering an objective response rate of 50 %, access to immunotherapy should be considered in these tumours.

Appendiceal adenocarcinoma is a rare malignancy with distinct histopathologic subtypes and a natural history with metastasis primarily limited to the peritoneum. Little is known about the molecular pathogenesis of appendiceal adenocarcinoma relative to common tumors.

We analyzed molecular data for patients within the Guardant Health database with appendix cancer (n = 718). We then identified patients with appendiceal adenocarcinoma at our institution (from October 2004-September 2022) for whom ctDNA mutation profiling (liquid biopsy) was performed (n = 168) and extracted clinicopathologic and outcomes data. Of these 168 patients, 57 also had tissue-based tumor mutational profiling, allowing for evaluation of concordance between liquid and tissue assays.

The mutational landscape of ctDNA in appendiceal adenocarcinoma is distinct from tissue-based sequencing, with TP53 being the most frequently mutated (46%). Relative to other tumors, appendiceal adenocarcinoma seems less likely to shed ctDNA, with only 38% of patients with metastatic appendiceal adenocarcinoma having detectable ctDNA (OR = 0.26; P < 0.0001 relative to colorectal cancer). When detectable, the median variant allele frequency was significantly lower in appendiceal adenocarcinoma (0.4% vs. 1.3% for colorectal cancer; P ≤ 0.001). High-grade, signet ring, or colonic-type histology, metastatic spread beyond the peritoneum, and TP53 mutation were associated with detectable ctDNA. With respect to clinical translation, patients with detectable ctDNA had worse overall survival (HR = 2.32; P = 0.048). In the Guardant Health cohort, actionable mutations were found in 93 patients (13.0%).

Although metastatic appendiceal adenocarcinoma tumors are less likely to shed tumor DNA into the blood relative to colorectal cancer, ctDNA profiling in appendiceal adenocarcinoma has clinical utility.

Pediatric high-grade glioma (pedHGG) can occur as first manifestation of cancer predisposition syndromes resulting from pathogenic germline variants in the DNA mismatch repair (MMR) genes MSH2, MSH6, MLH1, and PMS2. The aim of this study was to establish a generalized screening for Lynch syndrome and constitutional MMR deficiency (CMMRD) in pedHGG patients, as the detection of MMR deficiencies (MMRD) may enable the upfront therapeutic use of checkpoint inhibitors and identification of variant carriers in the patients' families. We prospectively enrolled 155 centrally reviewed primary pedHGG patients for MMR-immunohistochemistry (IHC) as part of the HIT-HGG-2013 trial protocol. MMR-IHC results were subsequently compared to independently collected germline sequencing data (whole exome sequencing or pan-cancer DNA panel next-generation sequencing) available in the HIT-HGG-2013, INFORM, and MNP2.0 trials. MMR-IHC could be successfully performed in 127/155 tumor tissues. The screening identified all present cases with Lynch syndrome or CMMRD (5.5%). In addition, MMR-IHC also detected cases with exclusive somatic MMR gene alterations (2.3%), including MSH2 hypermethylation as an alternative epigenetic silencing mechanism. Most of the identified pedHGG MMRD patients had no family history of MMRD, and thus, they represented index patients in their families. Cases with regular protein expression in MMR-IHC never showed evidence for MMRD in DNA sequencing. In conclusion, MMR-IHC presents a cost-effective, relatively widely available, and fast screening method for germline MMRD in pedHGG with high sensitivity (100%) and specificity (96%). Given the relatively high prevalence of previously undetected MMRD cases among pedHGG patients, we strongly recommend incorporating MMR-IHC into routine diagnostics.

Whether the progression of precursor lesions or the occurrence of cancer is influenced by lifestyle factors in carriers of genetic mutations has not been fully investigated, especially in Asian patients of hereditary colorectal cancer (CRC) syndrome.

Patients at a high risk of hereditary CRC were included. For polyposis CRC syndromes, colorectal polyp burden was measured using at least 60 images per colonoscopy in each patient and classified into five stages using the International Society for Gastrointestinal Hereditary Tumours staging system according to the polyp number and size. Increase in tumor burden stage for polyposis CRC syndrome and the occurrence of CRC or any cancer for Lynch syndrome were analyzed according to lifestyle factors.

Ninety-six patients with suspected hereditary polyposis CRC syndrome and 106 patients with Lynch syndrome were recruited. For polyposis CRC syndromes, multivariate analysis showed that exposure to smoking and > 100 polyps independently predicted a high risk of increased polyp burden (p = 0.008 and p = 0.012, respectively). Significant genetic mutations or phenotype of polyposis syndromes were significantly associated with an increased polyp burden. For Lynch syndrome, smokers showed to be diagnosed with CRC in younger age than never-smokers (42.2 years vs. 49.0 years; p = 0.021), and heavy drinkers had high risk for occurrence of CRC (HR, 2.381, 95% CI, 1.338-4.236; p = 0.003) and any cancer (HR, 2.254; 95% CI, 1.334-3.806; p = 0.002).

The lifestyle factors (smoking and alcohol consumption) were associated with increasing precursor lesions and occurrence of cancer in patients with hereditary CRC syndrome. Lifestyle modifications may reduce the risk of hereditary CRC in carriers.

Extramammary Paget's disease (EMPD) may be associated with an underlying internal adenocarcinoma, referred to as secondary EMPD. Differences in this association by EMPD anatomic subtype and implications for screening are not fully understood.

Define the rates of secondary EMPD and types of associated adenocarcinomas by EMPD anatomic subtype and propose a screening algorithm for underlying adenocarcinoma.

Systematic literature review of EMPD (January 1990-November 2022). One hundred twenty-two studies met the inclusion criteria. A multidisciplinary expert panel reviewed the recommendation statements on adenocarcinoma screening.

Perianal EMPD was associated with a high rate of underlying adenocarcinoma (25%, primarily colorectal) compared with penoscrotal and vulvar EMPD (6% each, primarily of genitourinary origin). Thorough screening in perianal EMPD includes a colonoscopy, urine cytology, and computed tomography of the chest, abdomen, and pelvis. Cost-conscious screening tests in low-risk penoscrotal disease include urine cytology, heme-occult test, and prostate-specific antigen test (especially if under 70 years of age). For low-risk vulvar EMPD, urine cytology and mammography are recommended. EMPD with high-risk features may warrant more sensitive organ-specific testing.

Selection bias; retrospective data without systematic follow-up.

Screening for underlying adenocarcinoma in EMPD should be guided by anatomic location.

Colorectal cancer (CRC) incidence and mortality before 50 have been rising alarmingly in the recent decades.

Using a cohort of 10,000 patients, this study investigates the clinical, mutational, and co-mutational features of CRC in early-onset (EOCRC, < 50 years) compared to late-onset (LOCRC, ≥ 50 years).

EOCRC was associated with a higher prevalence of Asian and Hispanic patients, rectal or left-sided tumors (72% vs. 59%), and advanced-stage disease. Molecular analyses revealed differences in mutation patterns, with EOCRC having higher frequencies of TP53 (74% vs. 68%, p < 0.01) and SMAD4 (17% vs. 14%, p = 0.015), while BRAF (5% vs. 11%, p < 0.001) and NOTCH1 (2.7% vs. 4.1%, p = 0.01) mutations were more prevalent in LOCRC. Stratification by tumor site and MSI status highlighted significant location- and age-specific molecular differences, such as increased KRAS and CTNNB1 mutations in right-sided EOCRC and higher BRAF prevalence in MSI-H LOCRC (47% vs. 6.7%, p < 0.001). Additionally, co-occurrence analysis revealed unique mutational networks in EOCRC MSS, including significant co-occurrences of FBXW7 with NOTCH3, RB1, and PIK3R1.

This study highlights the significance of age-specific molecular profiling, offering insights into the unique biology of EOCRC and potential clinical applications.