Prognostic Impact of Microsatellite Instability in Colorectal Cancer Presenting With Mucinous, Signet-Ring, and Poorly Differentiated Cells

Clinicopathological features and evaluation of microsatellite stability of colorectal carcinoma with cribriform comedo pattern

BACKGROUND

Cribriform comedo-type adenocarcinoma (CCA) was a colon cancer subtype defined in the 2009 World Health Organization (WHO) classification. In the 2018 classification, it was a colon cancer subtype included in the adenocarcinoma, Not otherwise specified (NOS) group. A few studies have reported that colon cancers with a cribriform pattern have worse overall survival, and most of them are microsatellite stable (MSS). In this study, we evaluated CCAs based on their clinicopathologic features and microsatellite stability. We aimed to answer whether these tumors could be defined as a distinct morphologic subtype with prognostic significance.

MATERIALS AND METHODS

Pathology reports and specimens from 449 patients with colorectal adenocarcinoma (CRA) were re-evaluated. All subtypes were determined. To evaluate MSS status, the CCA cases were immunohistochemically stained with anti-MLH1, MSH2, MSH6, and PMS2 antibodies.

RESULTS

CCA was present in 40.5% of cases. These cases were found to have higher rates of lymph node metastasis, lymphovascular-perineural invasion, metastasis, and advanced stage ( P < 0.05). Also, 2.7% of CCA cases were microsatellite instable (MSI). However, no statistically significant result was found regarding overall survival and progression-free survival of CCA cases with MSI.

CONCLUSION

According to the findings, CRAs with comedo cribriform patterns are tumors with more aggressive features. It can be said that these tumors have a specific molecular feature related to MSS. Because this feature is important for planning adjuvant chemotherapy, it may be useful to identify cases, particularly with a cribriform comedo pattern >90%. However, because no significant difference in survival rates was found, CCAs may not need to be defined as distinct subtypes.

Immunoexpression of Mismatch Repair Proteins in a Cohort of Colorectal Cancer Patients

One of the molecular routes of colorectal carcinogenesis is the lack of mismatch repair (MMR) proteins, which may have substantial clinical consequences in predicting therapy success. This study aimed to analyze the expression of the MutL homolog 1 (MLH1), MutS homolog 2 (MSH2), and MutS homolog 6 (MSH6) in a cohort of 91 colorectal cancer (CRC) patients, and to evaluate the relationship between patient clinicopathological characteristics and immunoexpression of these biomarkers. In this study, we obtained the highest scores of the MLH1 immunoexpression in non-mucinous tumors, moderately differentiated lesions, and in stage IV. The highest values of the MSH2 and MSH6 scores were observed in mucinous tumors, and poorly differentiated lesions, in stages II-III, and stages III-IV, respectively. To improve the stratification criteria for targeted oncological therapy and to predict patient outcomes, markers used may help evaluate the aggressiveness of lesions.

Correlation of clinical, pathologic, and genetic parameters with intratumoral immune milieu in mucinous adenocarcinoma of the colon

Mucinous adenocarcinoma (MAD), the most common subtype of colonic adenocarcinoma (CA), requires >50% intratumoral mucin. There is limited data regarding the impact of MAD on key lymphocyte subsets and therapeutically critical immune elements. In this study we address: (1) the definition of MAD, (2) grading of MAD, and (3) the impact of MAD and extracellular mucin on intratumoral immune milieu. Estimation of the percentage of intratumoral mucin was performed by two pathologists. Tissue microarrays were stained for immune markers including CD8, CD163, PD-L1, FoxP3, β2 microglobulin, HLA class I, and HLA class II. Immunohistochemistry for BRAF V600E was performed. MMR status was determined on immunohistochemistry for MSH2, MSH6, MLH1, PMS2. Manual and automated HALO platforms were used for quantification. The 903 CAs included 62 (6.9%) MAD and 841 CA with ≤ 50% mucin. We identified 225 CAs with mucinous differentiation, defined by ≥10% mucin. On univariate analysis neither cut point, 50% (p = 0.08) and 10% (p = 0.08) mucin, correlated with disease-specific survival (DSS). There were no differences in key clinical, histological and molecular features between MAD and CA with mucinous differentiation. On univariate analysis of patients with MAD, tumor grade correlated with DSS (p = 0.0001) while MMR status did not (p = 0.86). There was no statistically significant difference in CD8 (P = 0.17) and CD163 (P = 0.05) positive immune cells between MAD and conventional CA. However, deficient (d) MMR MADs showed fewer CD8 (P = 0.0001), CD163 (P = 0.0001) and PD-L1 (P = 0.003) positive immune cells compared to proficient (p)MMR MADs, a finding also seen with at 10% mucin cut point. Although MAD does not impact DSS, this study raises the possibility that the immune milieu of dMMR MADs and tumors with > =10% mucin may differ from pMMR MADs and tumors with <10% mucin, a finding that may impact immune-oncology based therapeutics.

The Molecular Associations of Signet-Ring Cell Carcinoma in Colorectum: Meta-Analysis and System Review

Background: Signet ring cell carcinoma (SC) accounts for 1% of total colorectal cancer (CRC) cases and is associated with aggressive behaviors, such as lymphatic invasion and distant metastases, resulting in poor prognosis. To date, there is still a lack of consensus on the genetic etiology underpinning this cancer subtype. This study aimed to clarify the molecular associations of SC by using meta-analysis and a systematic review. Methods: PubMed, Embase, and Cochrane Library were searched for studies evaluating the KRAS, BRAF, P53 statuses, and microsatellite instability (MSI) in CRC patients with different histological subtypes, including SC. The diagnosis of SC is defined as the signet ring cells comprising ≥50 percent of the tumor mass. By dividing the studies into subgroups based on the composition of control groups, such as classic adenocarcinoma (AC; no SC components) and non-SC (including those with SC components < 50%), the relative risk (RR) of molecular alterations for SC in each study were pooled using a random-effects model. Two reviewers identified trials for inclusion, assessed quality, and extracted data independently. Results: Data from 29 studies consisting of 9366 patients were included in this analysis. SC was associated positively with MSI (RR 1.78, 95% CI 1.34 to 2.37; 95% CI 0.77 to 4.15; p = 0.0005), BRAF mutation (RR 1.99, 95% CI 1.21 to 3.26; 95%CI 0.68 to 5.82; p = 0.0146), and negatively with KRAS mutation (RR 0.48, 95% CI 0.29 to 0.78; 95% CI 0.09 to 2.49; p = 0.0062). No association was found between SC and P53 expression (RR 0.92, 95% CI 0.76 to 1.13; 95%CI 0.61 to 1.39; p = 0.3790). Moreover, it was associated negatively with P53 gene mutations (RR 0.92, 95% CI 0.77 to 1.09; 95% CI 0.46 to 1.82; p = 0.1568), and P53 protein (RR 0.93, 95% CI 0.58 to 1.49; 95% CI 0.40 to 2.17; p = 0.6885). Conclusions: The molecular etiology of SC may be associated with the BRAF and MSI pathways. Its features, such as the high frequency of BRAF mutation, could partly explain its less favorable outcomes and limited effects of traditional chemotherapy.

Rate of dissemination and prognosis in early and advanced stage colorectal cancer based on microsatellite instability status: systematic review and meta-analysis

INTRODUCTION

For the past two decades, microsatellite instability (MSI) has been reported as a robust clinical biomarker associated with survival advantage attributed to its immunogenicity. However, MSI is also associated with high-risk adverse pathological features (poorly differentiated, mucinous, signet cell, higher grade) and exhibits a double-edged sword phenomenon. We performed a systematic review and meta-analysis to evaluate the rate of dissemination and the prognosis of early and advanced stage colorectal cancer based on MSI status.

METHODS

A systematic literature search of original studies was performed on Ovid searching MEDLINE, Embase, Cochrane Database of Systematic Reviews, American College of Physicians ACP Journal Club, Database of Abstracts of Reviews of Effects DARE, Clinical Trials databases from inception of database to June 2019. Colorectal cancer, microsatellite instability, genomic instability and DNA mismatch repair were used as key words or MeSH terms. The Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) reporting guideline was followed. Data were pooled using a random-effects model with odds ratio (OR) as the effect size. Statistical analysis was performed using RevMan ver 5.3 Cochrane Collaboration.

RESULTS

From 5288 studies, 136 met the inclusion criteria (n = 92,035; MSI-H 11,746 (13%)). Overall, MSI-H was associated with improved OS (OR, 0.81; 95% CI 0.73-0.90), DFS (OR, 0.73; 95% CI 0.66-0.81) and DSS (OR, 0.69; 95% CI 0.52-0.90). Importantly, MSI-H had a protective effect against dissemination with a significantly lower rate of lymph node and distant metastases. By stage, the protective effect of MSI-H in terms of OS and DFS was observed clearly in stage II and stage III. Survival in stage I CRC was excellent irrespective of MSI status. In stage IV CRC, without immunotherapy, MSI-H was not associated with any survival benefit.

CONCLUSIONS

MSI-H CRC was associated with an overall survival benefit with a lower rate of dissemination. Survival benefit was clearly evident in both stage II and III CRC, but MSI-H was neither a robust prognostic marker in stage I nor stage IV CRC without immunotherapy.

Assessment of mismatch repair deficiency, CDX2, beta-catenin and E-cadherin expression in colon cancer: molecular characteristics and impact on prognosis and survival - an immunohistochemical study

Microsatellite instability (MSI) or the deficiency of mismatch repair (MMR) proteins is one of the molecular pathways of colorectal tumorigenesis and may have important clinical implications in predicting the treatment response. We evaluated the relationship between clinicopathological features and MMR proteins [mutL homologue 1 (MLH1), mutS homologue 2 (MSH2), mutS homologue 6 (MSH6), postmeiotic segregation increased 2 (PMS2)], adhesion molecules (E-cadherin, beta-catenin) and caudal-type homeobox 2 (CDX2) in 31 patients with colon adenocarcinoma, using immunohistochemistry. We also aimed to assess the prognostic value of the studied proteins. MLH1 loss was correlated to PMS2 loss (p=0.006) and MSH2 loss (p=0.023); MSH2 loss was significantly associated to MSH6 loss (p=0.011). Tumors with MSH6 loss, together with tumors with PMS2 loss, covered all the patients with MSI status. We found a significant correlation between MSI tumors and mucinous histological type (p=0.03), but no significant associations with other clinicopathological features or with survival rate. There was a significant correlation between E-cadherin expression and differentiation degree (p=0.018) and between beta-catenin expression and lymph node invasion (p=0.046). No significant association between CDX2 loss and any clinical or pathological features was found (p>0.05). No significant differences were identified in overall survival according to E-cadherin, beta-catenin or CDX2 expression (p>0.05). In our study, PMS2 loss was significantly correlated with CDX2 loss (p=0.03). In conclusion, the molecular analysis of biological markers for colon cancer may be important for patient stratification, in order to select the optimal treatment algorithm. Our results suggest that probably the double panel (MSH6 and PMS2) is enough to detect the MSI status, instead of using the quadruple panel.

Implication of Microsatellite Instability in Chinese Cohort of Human Cancers

Background

Microsatellite instability (MSI) has been a hot topic in cancer research. Determining MSI status greatly aids tumor prognosis and treatment plans. However, MSI data for Asian cancer patients with prognostic information are scarce. Here, our aim was to clarify MSI status and its prognostic value in a large Chinese cohort with different tumors.

Patients and Methods

Tissue samples from 600 Chinese cases, including 150 endometrial cancers, 150 colorectal cancers, 150 liver cancers and 150 gastric cancers, were used for IHC and MSI examinations. Two mononucleotide and three dinucleotide markers were used to analyze MSI status.

Results

In total,17.3% (26/150) of endometrial cancer patients showed positive MSI,10.0% (15/150) in colorectal cancer, 2.7% (4/150) in liver cancer, and 2.7% (4/150) in gastric cancer. Tumor location (P < 0.001 for colorectal cancer) and clinical stage (P =0.038 for gastric cancer) showed significant correlations with MSI status in gastrointestinal carcinogenesis. The mismatch repair (MMR) deficiency was observed in 20 colorectal cases (13.3%) and was significantly more frequent in the MSI-positive group (P < 0.001). Interestingly, the prevalence of MSI-H was mostly occurred in early-stage tumors, and none was in late stage (stage IV). Meanwhile, low clinicopathological stage had significant correlation with longer survival in multiple cancers here.

Conclusion

The incidence of microsatellite instability varies among different cancer types. And the prevalence of MSI-H mostly occurred early clinicopathological stage. In addition, our study provided a large Asian cohort screened by five loci PCR method and significantly increased knowledge on the prognostic significance of MSI in Asia.

Tumour infiltrating lymphocyte status is superior to histological grade, DNA mismatch repair and BRAF mutation for prognosis of colorectal adenocarcinomas with mucinous differentiation

Mucinous colorectal adenocarcinoma (CRC) is conventionally defined by extracellular mucin comprising >50% of the tumour area, while tumours with ≤50% mucin are designated as having a mucinous component. However, these definitions are largely arbitrary and comparisons of clinico-molecular features and outcomes by proportion of mucinous component are limited. A cohort of 1643 patients with stage II/III cancer was examined for tumour mucinous component, DNA mismatch repair (MMR) status, BRAF mutation and tumour infiltrating lymphocytes (TILs). Tumours with ≤50% mucinous component exhibited similar characteristics as mucinous tumours, including association with female gender, proximal location, high grade, TIL-high, defective MMR (dMMR) and BRAF mutation. Proportion of mucinous component did not stratify disease-free survival (DFS). In univariate analysis dMMR status, but not histological grade, stratified survival for mucinous and mucinous component tumours; however, in multivariate analysis dMMR status was not an independent predictor. BRAF mutation prognostic value depended on mucinous differentiation and MMR status, with poor prognosis limited to non-mucinous pMMR tumours (HR 2.61, 95% CI 1.69-4.03; p < 0.001). TIL status was a strong independent predictor of DFS in mucinous/mucinous component tumours (HR 0.40, 95% CI 0.23-0.67; p < 0.001), and a superior predictor of prognosis compared with histological grade, MMR and BRAF mutation. Mucinous component and mucinous stage II/III CRCs exhibit clinico-molecular resemblances, with histological grade and BRAF mutation lacking prognostic value. Prognosis for these tumours was instead strongly associated with TIL status, with the most favourable outcomes in TIL-high dMMR tumours, whilst TIL-low tumours had poor outcomes irrespective of MMR status.

Prognostic value of KRAS mutation status in colorectal cancer patients: a population-based competing risk analysis

Background

To use competing analyses to estimate the prognostic value of KRAS mutation status in colorectal cancer (CRC) patients and to build nomogram for CRC patients who had KRAS testing.

Method

The cohort was selected from the Surveillance, Epidemiology, and End Results database. Cumulative incidence function model and multivariate Fine-Gray regression for proportional hazards modeling of the subdistribution hazard (SH) model were used to estimate the prognosis. An SH model based nomogram was built after a variable selection process. The validation of the nomogram was conducted by discrimination and calibration with 1,000 bootstraps.

Results

We included 8,983 CRC patients who had KRAS testing. SH model found that KRAS mutant patients had worse CSS than KRAS wild type patients in overall cohort (HR = 1.10 (95% CI [1.04–1.17]), p < 0.05), and in subgroups that comprised stage III CRC (HR = 1.28 (95% CI [1.09–1.49]), p < 0.05) and stage IV CRC (HR = 1.14 (95% CI [1.06–1.23]), p < 0.05), left side colon cancer (HR = 1.28 (95% CI [1.15–1.42]), p < 0.05) and rectal cancer (HR = 1.23 (95% CI [1.07–1.43]), p < 0.05). We built the SH model based nomogram, which showed good accuracy by internal validation of discrimination and calibration. Calibration curves represented good agreement between the nomogram predicted CRC caused death and actual observed CRC caused death. The time dependent area under the curve of receiver operating characteristic curves (AUC) was over 0.75 for the nomogram.

Conclusion

This is the first population based competing risk study on the association between KRAS mutation status and the CRC prognosis. The mutation of KRAS indicated a poor prognosis of CRC patients. The current competing risk nomogram would help physicians to predict cancer specific death of CRC patients who had KRAS testing.

Outcomes for Metastatic Colorectal Cancer Based on Microsatellite Instability: Results from the South Australian Metastatic Colorectal Cancer Registry

BACKGROUND

Microsatellite instability (MSI) is the molecular marker for DNA mismatch repair deficiency (dMMR) in colorectal cancer (CRC) and has been associated with better survival outcomes in early stage disease. In metastatic CRC (mCRC), outcomes for patients with MSI are less clear. There is evolving evidence that treatment pathways for MSI CRC should include programmed-death 1 (PD-1) antibodies.

OBJECTIVE

An analysis was performed to explore the impact of MSI status on overall survival (OS) in mCRC.

PATIENTS AND METHODS

South Australian Metastatic CRC Registry data were analysed to assess patient characteristics and survival outcomes, comparing patients with MSI CRC with those whose tumours were microsatellite stable (MSS). Kaplan-Meier survival analysis was used to assess OS. Cox regression analysis was undertaken to assess the independence of MSI as a prognostic factor.

RESULTS

Of 4359 patients registered on the database, 598 (14%) had been tested for, and 62 (10.1%) of these patients had, demonstrable MSI. There were significantly higher rates of right-sided primary (p < 0.001), poorly differentiated pathology (p = 0.002), and BRAF V600E mutation (p < 0.001) in the MSI group. The MSI group were also less likely to receive chemotherapy (p < 0.001) or to have liver surgery, but more likely to be diagnosed at an early stage. The median overall survival was 9.5 months for those with MSI CRC versus 21.3 months for MSS CRC patients (p = 0.052). Cox regression analysis indicated that MSI was not an independent predictor of OS. Independent predictors of better OS included having liver surgery for metastasis, having chemotherapy, and being initially diagnosed at an early stage.

CONCLUSIONS

Only 14% of patients with mCRC were tested for MSI, and 1 in 10 were found to be MSI high. The clinical characteristics of MSI mCRC are in keeping with those previously reported. MSI in this population-based registry was associated with a numerically lower survival which did not attain statistical significance.

Is microsatellite instability-high really a favorable prognostic factor for advanced colorectal cancer? A meta-analysis

Background

Stage II colorectal cancer with microsatellite instability-high (MSI-H) has been proven to have a better prognosis. However, in advanced stage, this trend remains controversial. This study aimed to explore the prognostic role of MSI-H in stage III and IV colorectal cancer (CRC) through meta-analysis.

Methods

A comprehensive search was performed in PubMed, Cochrane Central Library, and Embase databases. All randomized clinical trials and non-randomized studies were included based on inclusion and exclusion criteria and on survival after a radical operation with or without chemotherapy. The adjusted log hazard ratios (HRs) were used to estimate the prognostic value between MSI-H and microsatellite-stable CRCs. The random-effects model was used to estimate the pooled effect size.

Results

Thirty-six studies were included. Randomized controlled trials (RCT) and non-RCT were analyzed separately. For stage III CRCs, pooled HR for overall survival (OS) was 0.96 (95% confidence interval [CI] 0.75–.123) in the RCT subgroup and 0.89 (95% CI 0.62–1.28) in the non-RCT subgroup. For disease-free survival (DFS), the HR for the RCT group was 0.83 (95% CI 0.65–1.07), similar to the non-RCT subgroup (0.83, 95% CI 0.65–1.07). Disease-specific survival (DSS) was also calculated, which had an HR of 1.07 (95% CI 0.68–1.69) in the non-RCT subgroup. All these results showed that MSI-H has no beneficial effects in stage III CRC. For stage IV CRC, the HR for OS in the RCT subgroup was 1.23 (95% CI 0.92–1.64) but only two RCTs were included. For non-RCT study, the combined HR for OS and DFS was 1.10 (95% CI 0.77–1.51) and 0.72 (95% CI 0.53–0.98), respectively, suggesting the beneficial effect for DFS and non-beneficial effect for OS.

Conclusion

For stage III CRC, MSI-H had no prognostic effect for OS, DFS, and DSS. For stage IV CRC, DFS showed a beneficial result, whereas OS did not; however, the included studies were limited and needed further exploration.

SILAC-Based Quantification of TGFBR2-Regulated Protein Expression in Extracellular Vesicles of Microsatellite Unstable Colorectal Cancers

Microsatellite unstable (MSI) colorectal cancers (CRCs) are characterized by mutational inactivation of Transforming Growth Factor Beta Receptor Type 2 (TGFBR2). TGFBR2-deficient CRCs present altered target gene and protein expression. Such cellular alterations modulate the content of CRC-derived extracellular vesicles (EVs). EVs function as couriers of proteins, nucleic acids, and lipids in intercellular communication. At a qualitative level, we have previously shown that TGFBR2 deficiency causes overall alterations in the EV protein content. To deepen the basic understanding of altered protein dynamics, this work aimed to determine TGFBR2-dependent EV protein signatures in a quantitative manner. Using a stable isotope labeling with amino acids in cell culture (SILAC) approach for mass spectrometry-based quantification, 48 TGFBR2-regulated proteins were identified in MSI CRC-derived EVs. Overall, TGFBR2 deficiency caused upregulation of several EV proteins related to the extracellular matrix and nucleosome as well as downregulation of proteasome-associated proteins. The present study emphasizes the general overlap of proteins between EVs and their parental CRC cells but also highlights the impact of TGFBR2 deficiency on EV protein composition. From a clinical perspective, TGFBR2-regulated quantitative differences of protein expression in EVs might nominate novel biomarkers for liquid biopsy-based MSI typing in the future.

Signet ring cell colorectal cancer: genomic insights into a rare subpopulation of colorectal adenocarcinoma

Background

Signet ring cell carcinoma (SRCC) is a rare subtype of colorectal cancer (CRC). The aim of this study was to characterise the genomic alterations and outcomes of SRCC.

Methods

Medical records of metastatic CRC (mCRC) patients whose tumours were evaluated by NGS analysis were reviewed. SC-mCRC were classified into two groups: SRCC (>50% signet ring cells) and adenocarcinoma (AC) with SC component (≤50% signet ring cells).

Results

Six hundred and sixty-five mCRC patients were included. Of the 93 mCRC cases with SC features, 63 had slides for review. Of those 63 cases, 35 were confirmed SRCC, and 28 were AC with SC component. Compared with AC group, KRAS and PIK3CA mutations (mts) were found in only 11% (OR: 0.13) and 3% (OR: 0.15) of SRCC cases, respectively. In contrast to the 44% rate of APC mts in AC group, only 3% of SRCC patients had APC mts (OR = 0.04).

Conclusions

SRCC has distinct molecular features, including low rates of KRAS, PIK3CA and APC mts. Further study to identify activation pathways and potential therapeutic targets are needed.

Evaluation of Long-Term Outcomes of Microsatellite Instability Status in an Asian Cohort of Sporadic Colorectal Cancers

PURPOSE

Microsatellite instability in colorectal cancer (CRC) and its long-term outcomes remains poorly studied in Asians. We investigate the prognostic significance of microsatellite instability in an Asian population and assess its clinical impact in patients who undergo adjuvant chemotherapy.

METHODS

Six hundred fifty-four consecutive CRC patients who underwent surgical resection between January 2010 and December 2012 were recruited. Survival was estimated using the Kaplan-Meier approach. Univariate Cox proportional hazard models were used to estimate the hazard ratios for variables associated with survival. A subgroup analyses was performed for stage III patients who underwent chemotherapy to evaluate the prognostic significance of microsatellite instability in this group.

RESULTS

Five hundred ninety-one (90.4%) patients were microsatellite stable (MSS) while 63 (9.6%) were microsatellite instable (MSI). Three years recurrence-free survival (RFS) and disease-specific survival (DSS) were 83.7 versus 73.7% (p = 0.295) and 87.1 versus 91.2% (p = 0.307) in MSS and MSI tumors, respectively. Among stage III patients who received adjuvant therapy, MSI status was found to be an adverse prognostic factor for RFS (HR 2.74 (95% CI 1.43-5.26), p = 0.002). This remained significant on multivariate analysis (HR 2.38 (95% CI 1.15-4.93), p = 0.018). Adjuvant chemotherapy was associated with survival benefit for patients with MSS tumors (HR 0.35, 95% CI 0.17-0.69, p = 0.002) but not MSI tumors (HR 0.67, 95% CI 0.08-8.15, p = 0.750).

CONCLUSIONS

MSI status is not a prognostic indicator in the general CRC population but appears to be an adverse prognostic indicator for RFS in stage III CRC patients who received adjuvant chemotherapy.

Mismatch Repair Proteins and Microsatellite Instability in Colorectal Carcinoma (MLH1, MSH2, MSH6 and PMS2): Histopathological and Immunohistochemical Study

BACKGROUND

Colorectal cancer (CRC) is one of the most common cancers worldwide. Microsatellite instability (MSI) is detected in about 15% of all colorectal cancers. CRC with MSI has particular characteristics such as improved survival rates and better prognosis. They also have a distinct sensitivity to the action of chemotherapy.

AIM

The aim of the study was to detect microsatellite instability in a cohort of colorectal cancer Egyptian patients using the immunohistochemical expression of mismatch repair proteins (MLH1, MSH2, MSH6 and PMS2).

MATERIAL AND METHODS

Cases were divided into Microsatellite stable (MSS), Microsatellite unstable low (MSI-L) and Microsatellite unstable high (MSI-H). This Microsatellite stability status was correlated with different clinicopathological parameters.

RESULTS

There was a statistically significant correlation between the age of cases, tumor site & grade and the microsatellite stability status. There was no statistically significant correlation between the gender of patients, tumor subtype, stage, mucoid change, necrosis, tumor borders, lymphocytic response, lymphovascular emboli and the microsatellite stability status.

CONCLUSION

Testing for MSI should be done for all colorectal cancer patients, especially those younger than 50 years old, right sided and high-grade CRCs.