Should the grading of colorectal adenocarcinoma include microsatellite instability status?

[Quantification of CDX2 using H-Score and its prognostic value in colon cancer]

Colorectal cancer is the third tumor with the highest incidence in the world population and is the second cause of death according to the Globocan study. CDX2 has been acquiring an important role as a sensitive and specific marker in the diagnosis of colorectal cancer. However, the lack of inclusion of this marker in the pathology guidelines together with the lack of existing studies prevent its daily use. Although multiple studies relate the absence of staining to a worse prognosis, the literature does not define how intense the staining must be to be considered positive or negative. In the present study, the H-Score is described as a method to determine the positivity of CDX2 staining, using free access software called QuPath with a sample of 169 patients. Furthermore, it is suggested that those patients whose tumors had an H-Score for CDX2 less than or equal to 152 points had a significantly shorter recurrence-free interval time compared to those with an H-Score greater than this threshold. For this reason, this study aims to highlight the importance of quantification using digital pathology, as it could be applied in daily practice, and suggests a reference value for CDX2 from which the tumor prognosis may differ.

T2-weighted imaging-based radiomic-clinical machine learning model for predicting the differentiation of colorectal adenocarcinoma

BACKGROUND

The study on predicting the differentiation grade of colorectal cancer (CRC) based on magnetic resonance imaging (MRI) has not been reported yet. Developing a non-invasive model to predict the differentiation grade of CRC is of great value.

AIM

To develop and validate machine learning-based models for predicting the differentiation grade of CRC based on T2-weighted images (T2WI).

METHODS

We retrospectively collected the preoperative imaging and clinical data of 315 patients with CRC who underwent surgery from March 2018 to July 2023. Patients were randomly assigned to a training cohort (n = 220) or a validation cohort (n = 95) at a 7:3 ratio. Lesions were delineated layer by layer on high-resolution T2WI. Least absolute shrinkage and selection operator regression was applied to screen for radiomic features. Radiomics and clinical models were constructed using the multilayer perceptron (MLP) algorithm. These radiomic features and clinically relevant variables (selected based on a significance level of P < 0.05 in the training set) were used to construct radiomics-clinical models. The performance of the three models (clinical, radiomic, and radiomic-clinical model) were evaluated using the area under the curve (AUC), calibration curve and decision curve analysis (DCA).

RESULTS

After feature selection, eight radiomic features were retained from the initial 1781 features to construct the radiomic model. Eight different classifiers, including logistic regression, support vector machine, k-nearest neighbours, random forest, extreme trees, extreme gradient boosting, light gradient boosting machine, and MLP, were used to construct the model, with MLP demonstrating the best diagnostic performance. The AUC of the radiomic-clinical model was 0.862 (95%CI: 0.796-0.927) in the training cohort and 0.761 (95%CI: 0.635-0.887) in the validation cohort. The AUC for the radiomic model was 0.796 (95%CI: 0.723-0.869) in the training cohort and 0.735 (95%CI: 0.604-0.866) in the validation cohort. The clinical model achieved an AUC of 0.751 (95%CI: 0.661-0.842) in the training cohort and 0.676 (95%CI: 0.525-0.827) in the validation cohort. All three models demonstrated good accuracy. In the training cohort, the AUC of the radiomic-clinical model was significantly greater than that of the clinical model (P = 0.005) and the radiomic model (P = 0.016). DCA confirmed the clinical practicality of incorporating radiomic features into the diagnostic process.

CONCLUSION

In this study, we successfully developed and validated a T2WI-based machine learning model as an auxiliary tool for the preoperative differentiation between well/moderately and poorly differentiated CRC. This novel approach may assist clinicians in personalizing treatment strategies for patients and improving treatment efficacy.

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.

Clinical Features, Molecular Alterations and Prognosis of Colorectal Adenocarcinoma With Mucinous Component in Chinese Patients

Mucinous adenocarcinoma (MAC) is conventionally diagnosed by WHO definition when the extracellular mucin is >50% of the tumor area, while tumors with <50% mucin are designated as having a mucinous component. The study is aimed at analyzing the clinicopathologic characteristics, mutation spectrum, and prognosis of colorectal adenocarcinoma with mucinous component (CAWMC). Mutation analyses for exon 2 to 4 of KRAS gene and exon 15 of BRAF gene were performed by Sanger sequencing. Expression of DNA mismatch repairs and P53 proteins were evaluated by immunohistochemistry. Density of tumor-infiltrating lymphocyte (TIL) status was scored. We also evaluated the percentage of glands producing mucin and the morphology of the different tumor cell types in mucin pools. We retrospectively analyzed the prognosis of 43 patients with stage II/III. The overall frequencies of KRAS and BRAF mutations were 36% and 8%, respectively. Patients with MAC exhibiting high levels of mucin were related to the increase of tumor diameter (P=0.038) but were not associated with any of the other clinicopathologic parameters. The proportion or variable morphology of mucinous component did not stratify progression-free survival in stage II/III cases. TIL was the most significant predictor of progression-free survival among stage II/III CAWMC. It is interesting to note that signet ring cell carcinoma does not portend a worse prognosis for patients with high TIL levels. Combining use the grade of TIL status with the WHO grade of the entire tumor can help identify patients with a high risk of recurrence more accurately.

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.

Is medullary carcinoma of the colon underdiagnosed? An audit of poorly differentiated colorectal carcinomas in a large national health service teaching hospital

AIMS

Medullary carcinoma is an uncommon colorectal tumour which appears poorly differentiated histologically. Consequently, it may be confused with poorly differentiated adenocarcinoma not otherwise specified (NOS). The principal aim of this study was to review a large series of poorly differentiated colorectal cancers resected at a large National Health Service (NHS) Teaching Hospital to determine how often medullary carcinomas were misclassified . Secondary aims were to investigate how often neuroendocrine differentiation or metastatic tumours were considered in the differential diagnosis, and compare clinico-pathological features between medullary and poorly differentiated adenocarcinoma NOS.

METHODS AND RESULTS

Histology slides from 302 colorectal cancer resections originally reported as poorly differentiated adenocarcinoma were reviewed and cases fulfilling World Health Organisation (WHO) criteria for medullary carcinoma identified. The original pathology report was examined for any mention of medullary phenotype, consideration of neuroendocrine differentiation or consideration of metastasis from another site. Clinico-pathological features were compared to poorly differentiated adenocarcinoma NOS. Only one-third of medullary carcinomas were correctly identified between 1997 and 2018. The other two-thirds were reported as poorly differentiated adenocarcinoma NOS. The possibility of an extracolonic origin or neuroendocrine carcinoma was considered in 21 and 27% of reports. Most medullary carcinomas exhibited mismatch repair deficiency, were located in ascending colon and caecum and had a lower rate of vascular channel invasion and lymph node metastasis compared to poorly differentiated adenocarcinoma.

CONCLUSIONS

Medullary carcinoma of the colon is often mistaken for poorly differentiated adenocarcinoma NOS and occasionally for neuroendocrine or metastatic carcinoma. Greater familiarity with morphological criteria and use of mismatch repair protein staining should improve diagnosis.

Mismatch repair phenotype determines the implications of tumor grade and CDX2 expression in stage II-III colon cancer

Mismatch repair (MMR) deficiency is an indicator of good prognosis in localized colon cancer but also associated with lack of expression of caudal-type homeobox transcription factor 2 (CDX2) and high tumor grade; markers that in isolation indicate a poor prognosis. Our study aims to identify clinically relevant prognostic subgroups by combining information about tumor grade, MMR phenotype, and CDX2 expression. Immunohistochemistry for MMR proteins and CDX2 was performed in 544 patients with colon cancer stage II-III, including a cohort from a randomized trial. In patients with proficient MMR (pMMR) and CDX2 negativity, hazard ratio (HR) for cancer death was 2.93 (95% CI 1.23-6.99, p = 0.015). Cancer-specific survival for pMMR/CDX2-negative cases was 35.8 months (95% CI 23.4-48.3) versus 52.1-53.5 months (95% CI 45.6-58.6, p = 0.001) for the remaining cases (CDX2-positive tumors or deficient MMR (dMMR)/CDX2-negative tumors). In our randomized cohort, high tumor grade was predictive of response to adjuvant fluorouracil-levamisole in pMMR patients, with a significant interaction between tumor grade and treatment (p = 0.036). For pMMR patients, high tumor grade was a significant marker of poor prognosis in the surgery-only group (HR 4.60 (95% CI 1.68-12.61), p = 0.003) but not in the group receiving chemotherapy (HR 0.66 (95% CI 0.15-3.00), p = 0.587). To conclude, patients with pMMR and CDX2 negativity have a very poor prognosis. Patients with pMMR and high-graded tumors have a poor prognosis but respond well to adjuvant chemotherapy. CDX2 expression and tumor grade did not impact prognosis in patients with dMMR.

Overexpression of sortilin is associated with 5-FU resistance and poor prognosis in colorectal cancer

Colorectal cancer (CRC) is the third most common cancer worldwide. Even if 5-fluorouracil (5-FU) is used as the first-line chemotherapeutic drug, responsiveness is only 20-30%. Acquired resistance to 5-FU contributes to both poor patient prognosis and relapse, emphasizing the need to identify biomarkers. Sortilin, a vacuolar protein sorting 10 protein (Vps10p), implicated in protein trafficking, is over expressed in CRC cell lines cultured 72 hours in presence of 5-FU. This overexpression was also observed in 5-FU-resistant cells derived from these cell lines as well as in CRC primary cultures (or patients derived cell lines). A significantly higher expression of sortilin was observed in vivo, in 5-FU-treated tumours engrafted in Nude mice, as compared with non-treated tumour. A study of transcriptional regulation allowed identifying a decrease in ATF3 expression, as an explanation of sortilin overexpression following 5-FU treatment. In silico analysis revealed SORT1 expression correlation with poor prognosis. Moreover, sortilin expression was found to be positively correlated with CRC tumour grades. Collectively, our findings identify sortilin as a potential biomarker of 5-FU resistance associated with poor clinical outcomes and aggressiveness in CRC. As a new prognostic factor, sortilin expression could be used to fight against CRC.

Poorly differentiated clusters in colorectal cancer: a current review and implications for future practice

Poorly differentiated clusters (PDC), defined as small groups of ≥5 tumour cells without glandular differentiation, have gained recent attention as a promising prognostic factor in colorectal cancer (CRC). Numerous studies have shown PDC to be significantly associated with other adverse histopathological features and worse clinical outcomes. PDC may hold particular promise in stage II colon cancer, where risk stratification plays a critical role in patient selection for adjuvant chemotherapy. In addition, emerging evidence suggests that PDC can predict lymph node metastasis in endoscopically resected pT1 CRC, potentially helping the selection of patients for oncological resection. In 'head-to-head' comparisons, PDC grade has consistently outperformed conventional histological grading systems both in terms of risk stratification and reproducibility. With a number of large-scale studies now available, this review evaluates the evidence regarding the prognostic significance of PDC, considers its relationship with other emerging invasive front prognostic markers (such as tumour budding and stroma type), assesses its 'practice readiness', addressing issues such as interobserver reproducibility, scoring methodologies and special histological subtypes (e.g. micropapillary and mucinous carcinoma), and draws attention to ongoing challenges and areas in need of further study. Finally, emerging data on the role of PDC in non-colorectal cancers are briefly considered.

Label-free, automated classification of microsatellite status in colorectal cancer by infrared imaging

Challenging histopathological diagnostics in cancer include microsatellite instability-high (MSI-H) colorectal cancer (CRC), which occurs in 15% of early-stage CRC and is caused by a deficiency in the mismatch repair system. The diagnosis of MSI-H cannot be reliably achieved by visual inspection of a hematoxylin and eosin stained thin section alone, but additionally requires subsequent molecular analysis. Time- and sample-intensive immunohistochemistry with subsequent fragment length analysis is used. The aim of the presented feasibility study is to test the ability of quantum cascade laser (QCL)-based infrared (IR) imaging as an alternative diagnostic tool for MSI-H in CRC. We analyzed samples from 100 patients with sporadic CRC UICC stage II and III. Forty samples were used to develop the random forest classifier and 60 samples to verify the results on an independent blinded dataset. Specifically, 100% sensitivity and 93% specificity were achieved based on the independent 30 MSI-H- and 30 microsatellite stable (MSS)-patient validation cohort. This showed that QCL-based IR imaging is able to distinguish between MSI-H and MSS for sporadic CRC - a question that goes beyond morphological features - based on the use of spatially resolved infrared spectra used as biomolecular fingerprints.

Synchronous nodal metastatic risk in screening detected and endoscopically removed pT1 colorectal cancers

BACKGROUND

The population screening campaigns have resulted in increasing the prevalence of endoscopically resected colorectal cancers (CRCs) invading the submucosa (pT1). Synchronous nodal involvement occurs in less than 15 % of these tumors. Histologic criteria currently used for selecting patients needing resection are imprecise and most patients could have been simply followed-up. Tumor infiltrating lymphocytes (TILs) and mismatch repair (MMR) status impact on CRC prognosis. To identify patients requiring completion surgery, the value of histologic variables, TILs and MMR status as risk factors of nodal metastasis was investigated in screening detected and endoscopically removed pT1 CRCs.

METHODS

In 102 endoscopically resected pT1 CRCs, the cancer phenotype, CD3+ and CD8+ TILs, and MMR status were assessed. Univariate and multivariate analyses were used to evaluate the correlation with nodal metastasis.

RESULTS

Positive resection margin, evidence of vascular invasion and tumor budding, wide area of submucosal invasion, and high number of CD3+ TILs were associated with nodal metastasis in univariate analyses. Vascular invasion was statistically independent in multivariate analysis. Evidence of neoplastic cells in the vessels and/or at the excision border featured 5 out of 5 metastatic tumors and 13 out of 97 non-metastatic ones.

CONCLUSIONS

Completion surgery should be recommended only in pT1 CRC with vascular invasion or with tumor cells reaching the margin. In all other cases, the treatment choice should result from a multidisciplinary discussion on the patient-centered evaluation of the risk-benefit ratio.

CDH1 gene mutation in early-onset, colorectal signet-ring cell carcinoma

AIM

Colorectal signet-ring cell carcinomas (SRCC) are highly malignant tumours with poor prognosis that disproportionately affect younger patients. There is growing evidence of a unique set of molecular features that separate SRCC from conventional colorectal adenocarcinoma. Identification of these distinct features may have diagnostic and prognostic significance for patients and families. CDH1, which encodes E-cadherin, a cell adhesion protein, is commonly mutated in gastric SRCC and our study aimed to identify whether CDH1 mutation was also a common phenomenon in colorectal SRCC.

METHODS

DNA was extracted from formalin-fixed paraffin embedded tumour tissue, the CDH1 gene was analysed by next generation sequencing and the pathogenicity of mutations assessed in silico. Sections cut from the same blocks were immunostained to identify the presence of the E-cadherin protein.

RESULTS

We found 8 CDH1 mutations that meet our inclusion criteria in seven of 11 samples. Of these, five (from four patients), were likely to be germline mutations. E-cadherin staining was absent or markedly reduced in all of the seven samples with CDH1 mutation.

CONCLUSION

Our finding of CDH1 mutations in a proportion of signet-ring cell carcinomas and associated reduction in E-cadherin in these tumours supports previous findings of a role for mutation of this gene in the development of this disease. In addition, the finding of likely germline mutations suggests that a subset of these tumours may be familial. Loss of E-cadherin staining in the absence of CDH1 mutations however also suggests a role for environmental factors in a subset of these tumours.

Study of histopathologic parameters to define the prognosis of stage II colon cancer

PURPOSE

Stage II colon cancer (CC) represents a challenging scenario for the choice of adjuvant chemotherapy; here, histologic factors need to be weighed up to establish the risk of recurrence. Tumor budding (TB) has recently been indicated as a confident predictor of clinical outcome in CC. Likewise, the presence of poorly differentiated clusters (PDCs) in a tumor has been pointed out as a leading criterion of a tumor grading system. Our aim was to evaluate in patients with stage II CC the relationship between these features and clinical outcome.

PATIENTS AND METHODS

The study included 174 cases of stage II CC; histopathologic parameters such as TB, PDCs, microsatellite instability (MSI), and CDX2 expression were analyzed.

RESULTS

There were 107 (70.9%), 32 (21.2%), and 12 (7.9%) TB scored 1, 2, and 3 respectively; 113 (72.9%), 30 (19.4%), and 12 (7.7%) tumors showed grade 1, 2, and 3 PDCs respectively. A high-MSI was detected in 32 cases (18.4%) while CDX2 was negative in 20 (11.5%) tumor samples. In the whole study population, only the TB was found to be associated with disease-specific survival (P = 0.01). No parameter apart from age (P = 0.04) was a significant prognostic factor for overall survival (P < 0.05). Other commonly reported variables, including tumor size, degree of tumor differentiation, lymphovascular invasion, number of lymph nodes harvested ≥ 12, MSI, and PDCs, were not shown to have significant results.

CONCLUSIONS

Although confirmatory studies are awaited, our work supports the role of the TB in defining risk groups of the stage II CC.

Assessing colorectal cancer mismatch repair status in the modern era: a survey of current practices and re-evaluation of the role of microsatellite instability testing

Results of DNA mismatch repair testing are used to detect Lynch syndrome and have prognostic and therapeutic implications among patients with sporadic colorectal carcinomas. Immunohistochemistry for mismatch repair proteins (MLH1, PMS2, MSH2, MSH6) and PCR for microsatellite instability are two established methods for assessing mismatch repair function. Older literature suggested a discordance rate of approximately 5% between these assays, leading some institutions to perform dual testing on all cases. Although universal mismatch repair testing is now recommended by multiple professional organizations, none provide guidelines regarding preferred assays. We surveyed 96 academic and nonacademic institutions to assess Lynch syndrome screening practices and evaluated discordance rates between immunohistochemistry and PCR among 809 colorectal cancers tested in our own institution. Our survey demonstrated no significant differences between academic and nonacademic practices with respect to testing strategies. Eighty six percent performed universal screening, and usually (76%) employed immunohistochemistry on initial biopsy samples. Only 20% employed PCR; these were mostly academic practices that used both immunohistochemistry and PCR (p < 0.01 compared with the nonacademic groups). Loss of MLH1/PMS2 staining was often (90%) followed by either BRAF mutational analysis or MLH1 methylation assays. Only 24% adhered to WHO recommendations to assign histologic grade based on mismatch repair status. We found only 3 cases (0.4%) with discordant immunohistochemistry and PCR results in our own practice: 1 reflected decreased MSH-6 staining in a neoadjuvantly treated microsatellite stable tumor, 1 MLH1-deficient tumor showed diminished MLH1/PMS2 in the tumor compared with internal control, and 1 case reflected an error in the molecular laboratory. Overall, our results showed extremely low discordance between methods assessing mismatch repair status and would suggest immunohistochemistry as the preferred single screening test. PCR can be reserved for cases that show equivocal immunostaining patterns.

Prognostic Effect of Tumor Sidedness in Colorectal Cancer: A SEER-Based Analysis

BACKGROUND

The prognostic value of tumor sidedness in metastatic colorectal cancer (CRC) has been established, but its impact on nonmetastatic disease remains unclear. Our study aimed to explore the prognostic effect of tumor sidedness by subgroup survival analyses, according to histology and tumor grade in stage I-IV CRCs.

METHODS

A retrospective population-based study was conducted based on Surveillance, Epidemiology and End Results (SEER) data. Population data in the SEER 9 registry (1975-2014) were used to determine survival trends of CRCs, and associated population data in the SEER 18 registry (2000 to 2014) were used to assess the prognostic impact of tumor sidedness on CRCs.

RESULTS

The 5-year cause-specific survival for all subgroups of CRCs improved from 1975 to 2014. Of 238,826 patients, 44.2% had right-sided cancer. Patients with right-sided cancer were more likely to be older, to be women, to have disease of mucinous or signet-ring cell histology, to have more poorly differentiated tumors, and to be diagnosed with a more advanced disease stage. Multivariate Cox regression showed stage I-II right-sided cancers had better cause-specific survival than the left-sided cancers (left colon: hazard ratio [HR] = 1.091, 95% confidence interval [CI], 1.052-1.132; rectum: HR = 1.363; 95% CI, 1.304-1.425; P < .001), while stage III and IV right-sided cancers had worse cause-specific survival. In subgroup analyses by histology and tumor grade within stage III CRCs, right-sided poorly differentiated mucinous adenocarcinoma showed significantly better survival (left colon: HR = 1.352; 95% CI, 1.145-1.596; rectum: HR = 1.125; 95% CI, 0.916-1.381; P = .002).

CONCLUSION

The relationship between sidedness and prognosis in CRCs depends on stage and histopathologic characteristics, especially for stage III disease.

Clinical and Histopathologic Features of Colorectal Adenocarcinoma in Crohn's Disease

GOALS

The aim of this study was to assess the histopathologic characteristics of colorectal carcinomas (CRC) in patients with Crohn's disease (CD).

BACKGROUND

A higher frequency of microsatellite instability (MSI) is seen in mucinous compared with nonmucinous CRC which suggests that its pathogenesis involves distinct molecular pathways. Several publications reported a higher percentage of mucinous adenocarcinoma in CD patients with CRC. So far, there has been no investigation of MSI in CD patients with mucinous CRC.

STUDY

The medical records of patients who underwent surgery for CRC were reviewed and those with a history of CD identified. The data of histologic classification and MSI status of the tumor were investigated.

RESULTS

Fourteen patients with CD-associated CRC were identified (5 female, 9 male) resulting in 20 CRC in total. Histologic investigation revealed 7 adenocarcinomas without a mucinous or signet ring cell component. All other CRCs harbored a mucinous (n=11) and/or signet ring cell (n=6) component. All tumors assessed for MSI were found to be microsatellite stable.

CONCLUSIONS

Our data indicate that CRCs with signet ring cell and mucinous components were much more common in patients with CD than in patients with sporadic CRC. This observation suggests that CRC in CD represent an own entity with distinct histopathologic and molecular features. This may implicate potential consequences for diagnosis and therapy of CRC in CD in the future as well as new factors to identify patients with an increased risk for developing CRC in CD.

[Grading of tumors in the tubular digestive tract : Esophagus, stomach, colon and rectum]

Grading of tumors located in the tubular digestive tract is an integral component of pathology assessment reports but is subordinate to the histological typing of tumors with respect to the prognostic significance. Tumor grading has not been shown to be an independent prognostic marker for most tumor entities in the gastrointestinal tract; however, it may be relevant for further routine treatment decision making in early Union Internationale Contre le Cancer (UICC) stage cancers in which the prognosis for patients is less dominated by advanced tumor spread. Owing to the more favorable prognosis of microsatellite instability in colorectal cancer, the World Health Organization (WHO) has recommended that poorly differentiated tumors should be tested and graded as low grade (G1/G2) when microsatellite instability is detected. This recommendation has been integrated into the German S3 guidelines for colorectal cancers. Accordingly, microsatellite instability testing for grading purposes should become routine practice.

The current value of determining the mismatch repair status of colorectal cancer: A rationale for routine testing

Colorectal Cancer (CRC) is the third most prevalent cancer in men and women. Up to 15% of CRCs display microsatellite instability (MSI). MSI is reflective of a deficient mismatch repair (MMR) system and is most commonly caused by hypermethylation of the MLH1 promoter. However, it may also be due to autosomal dominant constitutional mutations in DNA MMR, termed Lynch Syndrome. MSI may be diagnosed via polymerase chain reaction (PCR) or alternatively, immunohistochemistry (IHC) can identify MMR deficiency (dMMR). Many institutions now advocate universal tumor screening of CRC via either PCR for MSI or IHC for dMMR to guide Lynch Syndrome testing. The association of sporadic MSI with methylation of the MLH1 promoter and an activating BRAF mutation may offer further exclusion criteria for genetic testing. Aside from screening for Lynch syndrome, MMR testing is important because of its prognostic and therapeutic implications. Several studies have shown MSI CRCs exhibit different clinicopathological features and prognosis compared to microsatellite-stable (MSS) CRCs. For example, response to conventional chemotherapy has been reported to be less in MSI tumours. More recently, MSI tumours have been shown to be responsive to immune-checkpoint inhibition providing a novel therapeutic strategy. This provides a rationale for routine testing for MSI or dMMR in CRC.

Diagnosing colorectal medullary carcinoma: interobserver variability and clinicopathological implications

Colorectal medullary carcinoma, recognized by the World Health Organization as a distinct histologic subtype, is commonly regarded as a specific entity with an improved prognosis and unique molecular pathogenesis. A fundamental but as yet unaddressed question, however, is whether it can be diagnosed reproducibly. In this study, by analyzing 80 colorectal adenocarcinomas whose dominant growth pattern was solid (thus encompassing medullary carcinoma and its mimics), we provided a detailed description of the morphological spectrum from "classic medullary histology" to nonmedullary poorly differentiated histologies and demonstrated significant overlapping between categories. By assessing a selected subset (n=30) that represented the spectrum of histologies, we showed that the interobserver agreement for diagnosing medullary carcinoma by using 2010 World Health Organization criteria was poor; the κ value among 5 gastrointestinal pathologists was only 0.157 (95% confidence interval, 0.127-0.263; P=.001). When we arbitrarily classified the entire cohort into "classic" and "indeterminate" medullary tumors (group 1, n=19; group 2, n=26, respectively) and nonmedullary poorly differentiated tumors (group 3, n=35), groups 1 and 2 were more likely to exhibit mismatch repair protein deficiency than group 3 (P<.001); however, improved survival could not be detected in either group compared with group 3. Our findings suggest that the diagnosis of medullary carcinoma, as currently applied, may only serve as a morphological descriptor indicating an increased likelihood of mismatch-repair deficiency. Additional evidence including a more objective classification system is needed before medullary carcinoma can be regarded as a distinct entity with prognostic relevance. Until such evidence becomes available, caution should be exercised when making this diagnosis, as well as when comparing results across different studies.

KRAS, NRAS, BRAF mutations and high counts of poorly differentiated clusters of neoplastic cells in colorectal cancer: observational analysis of 175 cases

A novel grading system based on the counting of poorly differentiated clusters (PDC) of neoplastic cells at the invasive margin and in the tumour stroma was recently introduced among the histological parameters predictive of adverse clinical outcome in colorectal cancer (CRC). The aim of this study was to correlate the histological grade based on PDC and the mutational status of KRAS, NRAS and BRAF genes in 175 consecutive CRCs. The highest PDC count under the objective lens of a ×20 microscopic field in each tumour was considered for grading assessment, so that PDC counts <5, 5-9 and ≥10 PDCs were defined grade 1, grade 2 and grade 3, respectively. Hotspots mutations were identified using the MassArray platform. Overall, there were 42 (24%) mutated tumours. Mutational status was significantly associated with high pT stage (p = 0.0021), advanced pTNM stage (p = 0.0018), nodal metastases (p = 0.006), tumour budding (p = 0.022) and high PDC grade (p = 0.0022). KRAS mutations were significantly associated with PDC grade (p = 0.0379), while BRAF mutations were associated with PDC-G3 although statistical significance was not reached. No significant associations were found between NRAS and PDC. The significant association between mutated KRAS and PDC grade suggests that KRAS mutations may be involved in the formation of PDC.

Microsatellite instability is associated with reduced disease specific survival in stage III colon cancer

BACKGROUND

Up to 15% of colorectal cancers exhibit microsatellite instability (MSI), where errors in replication go unchecked due to defects in the mismatch repair system. This study aimed to determine survival in a large single-centre series of 1250 consecutive colorectal cancers subjected to universal MSI testing.

METHODS

Clinical and pathological features of patients with colorectal cancer identified on prospectively maintained colorectal and pathology databases at St. Vincent's University Hospital from 2004 to May 2012 were examined. Mismatch repair (MMR) status was determined by immunohistochemistry. Kaplan-Meier curves, the log-rank test and Cox regression were used to associate survival with clinical and pathological characteristics.

RESULTS

Of the 1250 colorectal cancers in the study period, 11% exhibited MSI (n = 138). Patients with MSI tumours had significantly lower rates of lymph node and distant metastases (MSI N+ rate: 24.8% compared with MSS N+ rate: 46.2%, p < 0.001). For Stage I and II disease MSI was associated with improved disease free survival (DSS) compared with MSS colon cancer. However, patients with Stage III MSI colon cancers had a worse DSS than those with MSS tumours. Stage III MSI tumours exhibited higher rates of lymphovascular invasion and perineural invasion than Stage I/II MSI tumours.

CONCLUSION

MSI is associated with a reduced risk of nodal and distant metastases, with an improved DSS in Stage I/II colon cancer. However, when MSI tumours progress to Stage III these patients had worse outcomes and pathological features. New strategies for this cohort of patients may be required to improve outcomes.

A novel histologic grading scheme based on poorly differentiated clusters is applicable to treated rectal cancer and is associated with established histopathological prognosticators

The conventional histologic grading of colorectal cancer (CRC) is less suited for resected rectal cancer following neoadjuvant chemoradiation. Enumeration of poorly differentiated clusters (PDC) is a recently proposed histologic grading scheme. We aimed to apply PDC grading to treated rectal cancer and to test the prognostic significance of this novel approach. Archived hematoxylin and eosin slides of 72 rectal adenocarcinomas resected following neoadjuvant treatment were retrieved. PDC, tumor budding, and tumor regression were assessed. The parameters were correlated with clinicopathological features and survival. PDC was strongly associated with tumor budding, perineural invasion (PNI), metastasis, and low degree of tumor regression. Tumor budding was significantly associated with lymphovascular invasion and PNI, and metastasis. Tumors with a lower degree of regression were more likely to show high pathologic T stage and advanced clinical stage. Local recurrence was associated with poor survival. PDC did not correlate with overall survival. PDC grading is applicable to resected rectal cancer status post neoadjuvant treatment and correlates with established histopathological prognosticators. PDC and tumor budding may represent a histologic spectrum reflective of the same biological significance. Validation and incorporation of these simple histologic grading schemes may strengthen the prognostic power of the histologic parameters that influence the oncologic outcome in treated rectal cancer. Further study to evaluate the significance of PDC as an oncologic prognosticator is warranted.

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

Purpose

Mucinous cells (MUCs), signet-ring cells (SRCs), and poorly differentiated cells (PDCs) are uncommon histologic types and have been associated with advanced tumor stage and poor prognosis. However, MUCs, SRCs, and PDCs are commonly observed in cancers with high microsatellite instability (MSI), which have favorable outcomes compared with cancers with microsatellite stability (MSS). The purpose of this study was to evaluate the prognostic impact of high-MSI in patients with sporadic colorectal cancer presenting with MUCs, SRCs, and/or PDCs.

Methods

Between January 2006 and December 2012, 176 with proven microsatellite status who also presented with MUCs, SRCs, and PDCs were selected for this study and were divided into 2 groups, high-MSI and MSS; their outcomes were analyzed.

Results

Of the 176 patients, 56 and 120, respectively, had high-MSI and MSS cancers. High-MSI cancers had larger tumors, proximal tumor location, and a lower TNM stage. The recurrence rate was lower in the high-MSI group (13.7% vs. 35.4%, P = 0.006). Common patterns of distant metastasis for MUC, SRC, PDC cancers were peritoneal spread (46.9%) and hematogenous metastasis (46.4%). The 5-year CSS rates were 88.2% and 61.2% for patients with high-MSI and MSS cancers, respectively (P < 0.0001). In the multivariate analysis, except for stage-IV cancer, MSI status was an independent risk factor for cancer-specific survival (MSS: hazard ratio, 4.34; 95% confidence interval, 1.68-11.21).

Conclusion

In patients with colorectal cancer presenting with MUCs, SRCs, and/or PDCs, those with high-MSI cancers had better outcomes.

Mismatch repair deficiency as a prognostic factor in mucinous colorectal cancer

There is some uncertainty about pathological grading of mucinous colorectal adenocarcinoma, defined as colorectal cancer demonstrating at least 50% mucinous differentiation. Under the WHO 2000 classification mucinous colorectal cancer was considered high grade. However under the current WHO 2010 classification microsatellite unstable/mismatch repair-deficient (MSI/MMRd) mucinous colorectal cancer is considered low grade, whereas microsatellite stable/mismatch repair proficient (MSS/MMRp) tumours are high grade. However there is little empirical evidence for this approach. We therefore compared the long term survival of patients with MSI/MMRd vs MSS/MMRp mucinous colorectal cancer in a large unselected cohort of patients undergoing surgery at our institution from 1998 to 2011. There were 2608 patients in the cohort, of which 264 (10.1%) were mucinous. 95 (36%) of the mucinous tumours were microsatellite unstable. The all-cause 5-year survival of mucinous MSI/MMRd colorectal cancer was similar to that of non-mucinous low-grade colorectal cancer (73 vs 67%, P=0.368), and significantly better than that of both non-mucinous high-grade (73 vs 53%, P<0.001) and mucinous MSS/MMRp colorectal cancer (73 vs 57%, P=0.023). The 5-year survival of mucinous MSS/MMRp colorectal cancer was slightly better than that of non-mucinous high-grade patients (57 vs 53%, P=0.027), but significantly worse than that of non-mucinous low-grade colorectal cancer (57 vs 67%, P=0.018). In multivariate Cox regression analysis, conventional histological grade based on glandular differentiation maintained prognostic significance (P=0.003) whereas MSI/MMRd status just failed to be statistically significant (P=0.062). Our findings support the WHO 2010 approach that as a group mucinous MSS/MMRp colorectal cancers are biologically aggressive. However, grading based exclusively on MSI/MMR status may be overly simplistic as conventional grading based on the degree of glandular differentiation still holds greater prognostic significance in multivariate analysis.

Histologic prognostic markers in stage IIA colorectal cancer: a comparative study

OBJECTIVE

pTNM stage IIA colorectal cancer (CRC) is not currently submitted to any adjuvant treatment due to its good prognosis. Nevertheless, a percentage of cases unexpectedly recur. The aim of this study was to assess and compare the prognostic value and inter-observer agreement of a novel histological grading system based on the counting of poorly differentiated clusters (PDC) of cancer cells and that of conventional histological grade, lymphatic, venous and perineural invasion (LVI, VI, PNI), tumour budding (TB) and tumor border configuration in stage IIA CRC.

MATERIALS AND METHODS

the afore mentioned histological parameters were assessed in 82 stage IIA CRCs. Inter-observer agreement and correlation with tumour relapse were analyzed by using Fleiss-Cohen's weighted K statistics, Fisher exact test and Chi-squared test. The Mantel-Cox log-rank test was applied to assess the strength of association with disease-free interval (DFI).

RESULTS

inter-observer agreement was very good/good in the assessment of PDC presence and grade, while it was moderate at best in the evaluation of the other parameters. The presence of PDC, high PDC grade, LVI and TB were significantly associated with disease progression (p < 0.0001; p = 0.0012; p = 0.0308; p = 0.0002) and shorter DFI (p = 0.0001; p < 0.0001; p = 0.0129; p = 0.0008). PDC presence (p < 0.0001) and TB (p = 0.012) were independent prognostic factors in multivariate analysis.

CONCLUSIONS

our findings suggest that the assessment of PDC may be useful to stratify patients with stage IIA CRC for recurrence risk, and to identify high risk patients who could benefit from adjuvant chemotherapy.

Adverse histological features in malignant colorectal polyps: a contemporary series of 239 cases

AIMS

Screening colonoscopy has led to more colorectal carcinomas presenting at an early stage potentially curable by endoscopic resection. In this study, we examined the clinical and histological features of a contemporary series of malignant colorectal polyps (MCPs) with subsequent surgical resection.

METHODS

We conducted a retrospective study on a consecutive series of MCPs from 239 patients, predominantly males (57.7%) with a median age of 66 years, and assessed histological parameters associated with residual disease on the surgical specimens.

RESULTS

Median MCP size was 18.6 mm, with 23.1% polyps measuring ≤10 mm. From the 140 surgical resection specimens, residual disease was identified in 20 cases, including 12 cases with metastatic lymph nodes and/or 9 cases with residual carcinoma in the large bowel wall. Histological parameters associated with nodal metastases were greater width and greater depth of the invasive component (p=0.001 and 0.006, respectively), poor differentiation (p=0.003) and a cribriform pattern (p=0.01). The risk of nodal metastases was 23.3% if two or three of these features were identified, while it was 0% and 4.5% if none or one was present, respectively. A positive margin was not associated with nodal metastasis and might be adequately treated by local endoscopic resection.

CONCLUSIONS

Surgical resection should be recommended if ≥2 of these adverse histological features are present and may be warranted if one feature is present. A positive margin may require additional local resection but not necessarily surgery if no other adverse factors are present.

Prognostic significance of grading based on the counting of poorly differentiated clusters in colorectal mucinous adenocarcinoma

Mucinous adenocarcinoma (MAC) of the colon and rectum is a histological entity with still indefinite prognostic significance. Although it was previously designated as poorly differentiated by convention, the most recent World Health Organization guidelines indicate that the level of maturation of the epithelium determines differentiation in MAC and that microsatellite instability status should be taken into account for its histological grading. Nonetheless, precise criteria for grading are not provided, and the prognostic value of histological grading in MAC still remains unclear. In the present study we aimed to investigate the prognostic value of a grading system based on the counting of poorly differentiated clusters (PDC) of neoplastic cells in 108 colorectal MACs and to compare its reproducibility and significance with those of a grading system based on glandular differentiation. We found that PDC grade was more reproducible and significantly associated with disease progression (P = .0089) as well as with death from colorectal cancer (P = .0035) in our MACs, as compared to the grade based on glandular differentiation, which was not associated with any of the clinicopathologic variables. Moreover, PDC grade emerged as a significant, independent prognostic factor of recurrence-free survival (P = .0198) and cancer-specific survival (P = .0293) in MAC. Interestingly, the prognostic value of PDC grade was unaltered following incorporation of mismatch repair system status in grading. In conclusion, we demonstrated for the first time that PDC grading is feasible, reproducible, and prognostically relevant in MAC, which may support its use in routine practice.

Personalizing colon cancer adjuvant therapy: selecting optimal treatments for individual patients

For more than three decades, postoperative chemotherapy-initially fluoropyrimidines and more recently combinations with oxaliplatin-has reduced the risk of tumor recurrence and improved survival for patients with resected colon cancer. Although universally recommended for patients with stage III disease, there is no consensus about the survival benefit of postoperative chemotherapy in stage II colon cancer. The most recent adjuvant clinical trials have not shown any value for adding targeted agents, namely bevacizumab and cetuximab, to standard chemotherapies in stage III disease, despite improved outcomes in the metastatic setting. However, biomarker analyses of multiple studies strongly support the feasibility of refining risk stratification in colon cancer by factoring in molecular characteristics with pathologic tumor staging. In stage II disease, for example, microsatellite instability supports observation after surgery. Furthermore, the value of BRAF or KRAS mutations as additional risk factors in stage III disease is greater when microsatellite status and tumor location are taken into account. Validated predictive markers of adjuvant chemotherapy benefit for stage II or III colon cancer are lacking, but intensive research is ongoing. Recent advances in understanding the biologic hallmarks and drivers of early-stage disease as well as the micrometastatic environment are expected to translate into therapeutic strategies tailored to select patients. This review focuses on the pathologic, molecular, and gene expression characterizations of early-stage colon cancer; new insights into prognostication; and emerging predictive biomarkers that could ultimately help define the optimal adjuvant treatments for patients in routine clinical practice.

Medullary colorectal carcinoma revisited: a clinical and pathological study of 102 cases

AIM

Medullary carcinoma is a recently described subtype of mismatch repair deficient (MMRd) colorectal carcinoma (CRC) which, despite being poorly differentiated by traditional morphological criteria, has been reported to have a good prognosis. We investigated the pathological and clinical features of medullary CRC in an unselected cohort of CRCs undergoing surgical resection.

METHODS

All CRCs resected within a single health district database from 1998 to 2012 were categorized prospectively and underwent retrospective review to identify 91 medullary CRCs, with 11 additional cases from 2013 to 2014. Strict criteria were employed to diagnose medullary carcinoma requiring both MMRd and greater than 90 % of the tumor to demonstrate typical morphology, including solid growth. The demographic and pathological features, as well as all-cause survival, were compared with other CRCs, and specifically to other MMRd CRCs.

RESULTS

From 1998 to 2012, 91 of 3,295 CRCs (2.8 %) were of the medullary type. Medullary CRC was more likely to arise in females than males (3.3:1; p < 0.0001), the elderly (mean age 77 vs. 71 years; p < 0.001), and the right colon (86 %; p < 0.0001). All medullary CRCs demonstrated MMR deficiency (considered an inclusion criteria) and 86 % were BRAFV600E-mutated (p < 0.0001). Thirty-day mortality after resection was higher in medullary CRC (4.6 vs. 1.7 %; p = 0.049). On univariate analysis, survival was not better than well-differentiated or other MMRd tumors. However, using a multivariate model, a medullary phenotype was protective (hazard ratio of death 0.54, 95 % CI 0.30-0.96; p = 0.037).

CONCLUSIONS

Medullary CRC is more common than previously reported, frequently presents with locally advanced disease, and may be associated with higher mortality at 30 days after resection. Despite this, when strict criteria are used for diagnosis, the overall survival is favorable when compared with CRCs with equivalent demographic and pathological characteristics.