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Both lymph node metastases (LNMs) and tumour deposits (TDs) are included in colorectal cancer (CRC) staging, although knowledge regarding their biological background is lacking. This study aimed to compare the biology of these prognostic features, which is essential for a better understanding of their role in CRC spread. Spatially resolved transcriptomic analysis using digital spatial profiling was performed on TDs and LNMs from 10 CRC patients using 1,388 RNA targets, for the tumour cells and tumour microenvironment. Shotgun proteomics identified 5,578 proteins in 12 different patients. Differences in RNA and protein expression were analysed, and spatial deconvolution was performed. Image‐based consensus molecular subtype (imCMS) analysis was performed on all TDs and LNMs included in the study. Transcriptome and proteome profiles identified distinct clusters for TDs and LNMs in both the tumour and tumour microenvironment segment, with upregulation of matrix remodelling, cell adhesion/motility, and epithelial–mesenchymal transition (EMT) in TDs (all p < 0.05). Spatial deconvolution showed a significantly increased abundance of fibroblasts, macrophages, and regulatory T‐cells (p < 0.05) in TDs. Consistent with a higher fibroblast and EMT component, imCMS classified 62% of TDs as poor prognosis subtype CMS4 compared to 36% of LNMs (p < 0.05). Compared to LNMs, TDs have a more invasive state involving a distinct tumour microenvironment and upregulation of EMT, which are reflected in a more frequent histological classification of TDs as CMS4. These results emphasise the heterogeneity of locoregional spread and the fact that TDs should merit more attention both in future research and during staging. © 2023 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland. [ABSTRACT FROM AUTHOR]

Virtual pathology education has shown to enhance the students' learning experience. At the Radboud University, an E‐learning platform—called the "PathoDiscovery"—was developed and first used in a course about neoplasm development amongst first year (bio)medical sciences students. The PathoDiscovery incorporates high‐power microscopic images, histological annotations, interactive questions and pre‐programmed feedback.The objective of our study was to develop and evaluate the PathoDiscovery within the "Neoplasm" course focusing on student perceptions of usability and utility. For this study the online feedback on the PathoDiscovery that was obtained anonymously from (bio)medical students over two consecutive academic years was analyzed. The responses of the first year were used to make improvements. After the second year, the feedback of the two academic years was compared. The rating of the E‐learning increased from 6.8 (n = 285) to 7.4 (n = 247) after implementation of feedback obtained in the first year. The students judged the structure as logical (90%). The content was considered easy or just right (57%), matched the learning objectives (76%), and contributed to knowledge development (78%). We conclude that the first experiences with the PathoDiscovery are positive for both students and lecturers; it is an example of a dynamic online learning tool that is easily adaptable and is well suited for a blended learning approach. [ABSTRACT FROM AUTHOR]

Tumor budding (TB) is a strong biomarker of poor prognosis in colorectal cancer and other solid cancers. TB is defined as isolated single cancer cells or clusters of up to four cancer cells at the invasive tumor front. In areas with a large inflammatory response at the invasive front, single cells and cell clusters surrounding fragmented glands are observed appearing like TB. Occurrence of these small groups is referred to as pseudobudding (PsB), which arises due to external influences such as inflammation and glandular disruption. Using a combination of orthogonal approaches, we show that there are clear biological differences between TB and PsB. TB is representative of active invasion by presenting features of epithelial‐mesenchymal transition and exhibiting increased deposition of extracellular matrix within the surrounding tumor microenvironment (TME), whereas PsB represents a reactive response to heavy inflammation where increased levels of granulocytes within the surrounding TME are observed. Our study provides evidence that areas with a strong inflammatory reaction should be avoided in the routine diagnostic assessment of TB. © 2023 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland. [ABSTRACT FROM AUTHOR]

Umbilical metastases form a clinical challenge, especially when they represent the first sign of malignant disease and the primary tumor is unknown. Our study aims to generate insight into the origin and timing of umbilical metastasis, as well as patient survival, using population‐based data. A nationwide review of pathology records of patients diagnosed with an umbilical metastasis between 1979 and 2015 was performed. Data was collected from the Nationwide Network and Registry of Histopathology and Cytopathology (PALGA) and the Netherlands Cancer Registry. Kaplan‐Meier analyses and log‐rank testing were used to estimate overall survival and a Cox proportional hazard model was used to determine multivariable hazard ratios. A total of 806 patients with an umbilical metastasis were included. There were 210 male (26.1%) and 596 female (73.9%) patients. Distribution of umbilical metastases was different between male and female patients due to the high incidence of umbilical metastases originating from the ovaries in females. They most frequently originated from the ovaries in female patients (38.8%) and from the colon in male patients (43.8%). In 18% of cases no primary tumor could be identified. Prognosis after diagnosis of an umbilical metastasis was dismal with a median survival of 7.9 months (95% confidence interval 6.7‐9.1). The origin of the primary tumor was an independent prognostic factor for overall survival. In conclusion, umbilical metastases relatively rare, mainly originating from intraabdominal primary tumors. Survival is dependent on the origin of the primary tumor and poor overall survival rates warrant early recognition. What's new? Umbilical metastases are a rare consequence of malignant disease that pose unique clinical challenges. Very little is known about these metastases, especially regarding incidence and survival. This population‐based analysis of more than 800 patients in the Netherlands shows that the distribution in umbilical metastases differs between males and females. In females, metastases most commonly originated from the ovaries, while in males, the colon was most common. Umbilical metastases, however, were linked to a variety of primary tumors and were frequently diagnosed synchronously with the primary tumor. While prognosis was poor overall, survival was influenced by primary tumor origin. [ABSTRACT FROM AUTHOR]

Aims: RNF43 is suggested to be involved in the serrated pathway towards colorectal cancer and encodes a transmembrane Ring‐type E3 ubiquitin ligase that negatively regulates the Wnt pathway. This study aimed to elucidate the role of RNF43 gene variants in serrated polyposis syndrome (SPS) and serrated polyps. Methods and results: Three cohorts were tested. The first cohort included germline DNA of 26 SPS patients tested for pathogenic variants in RNF43 by Sanger sequencing all exons. In the second cohort we tested somatic DNA for RNF43 mutations from sporadic serrated lesions: 25 hyperplastic polyps, 35 sessile serrated lesions and 38 traditional serrated adenomas (TSA). In the third cohort we investigated RNF43 mutations in 49 serrated polyps and 60 conventional adenomas from 40 patients with Lynch syndrome. No germline RNF43 pathogenic variants were detected in our SPS cohort. In sporadic colorectal lesions we detected RNF43 deleterious frameshift mutations in three TSA and one SSL. The RNF43 mutations in previously described homopolymeric hot‐spots were detected in microsatellite‐instable (MSI) polyps and the other RNF43 mutations in microsatellite‐stable (MSS) serrated polyps. RNF43 hot‐spot mutations were discovered in seven serrated polyps and 12 conventional adenomas from Lynch patients. Conclusion: Truncating germline RNF43 mutations are uncommon in SPS patients. Somatic mutations in RNF43 were found in sporadic TSA and SSL and both serrated polyps and adenomas from Lynch syndrome patients, suggesting that they do not develop early in the pathway to CRC and are not specific for serrated polyp subtypes. [ABSTRACT FROM AUTHOR]

Aims: Outcomes of colorectal cancer (CRC) treatment and survival have steadily improved during the past decades, accompanied by an increased risk of developing second primary tumours and metastatic tumours at unusual sites. Metastatic CRC can show mucosal colonisation, thereby mimicking a second primary tumour. This potential confusion could lead to incorrect diagnosis and consequently inadequate treatment of the patient. The aim of this study was to differentiate between metastatic CRC and a second primary (gallbladder cancer, GBC) using a combination of standard histopathology and molecular techniques. Methods and results: Ten consecutive patients with both CRC and GBC were identified in our region using the Dutch National Pathology Archive (PALGA). Two patients served as negative controls. Histology of GBC was reviewed by nine pathologists. A combination of immunohistochemistry, microsatellite analysis, genomewide DNA copy number analysis and targeted somatic mutation analysis was used to aid in differential diagnosis. In two patients, CRC and GBC were clonally related, as confirmed by somatic mutation analysis. For one case, this was confirmed by genomewide DNA copy number analysis. However, in both cases, pathologists initially considered the GBC as a second primary tumour. Conclusions: Metastatic CRC displaying mucosal colonisation is often misinterpreted as a second primary tumour. A combination of traditional histopathology and molecular techniques improves this interpretation, and lowers the risk of inadequate treatment. [ABSTRACT FROM AUTHOR]

RNA interference (RNAi) is widespread in eukaryotes and regulates gene expression transcriptionally or post-transcriptionally. In fission yeast, RNAi is tightly coupled to template transcription and chromatin modifications that establish heterochromatin in cis. Exogenous double-stranded RNA (dsRNA) triggers seem to induce heterochromatin formation in trans only when certain silencing proteins are overexpressed. Here, we show that green fluorescent protein (GFP) hairpin dsRNA allows production of high levels of Argonaute-associated small interfering RNAs (siRNAs), which can induce heterochromatin formation at a remote locus. This silencing does not require any manipulation apart from hairpin expression. In cells expressing a ura4+–GFP fusion gene, production of GFP siRNAs causes the appearance of ura4 siRNAs from the target gene. Production of these secondary siRNAs depends on RNA-dependent RNA polymerase Rdp1 (RDRPRdp1) function and other RNAi pathway components. This demonstrates that transitivity occurs in fission yeast and implies that RDRPRdp1 can synthesize RNA from targeted RNA templates in vivo, generating siRNAs not homologous to the hairpin. [ABSTRACT FROM AUTHOR]

The formation of heterochromatin at the centromeres in fission yeast depends on transcription of the outer repeats. These transcripts are processed into siRNAs that target homologous loci for heterochromatin formation. Here, high throughput sequencing of small RNA provides a comprehensive analysis of centromere-derived small RNAs. We found that the centromeric small RNAs are Dcr1 dependent, carry 5′-monophosphates and are associated with Ago1. The majority of centromeric small RNAs originate from two remarkably well-conserved sequences that are present in all centromeres. The high degree of similarity suggests that this non-coding sequence in itself may be of importance. Consistent with this, secondary structure-probing experiments indicate that this centromeric RNA is partially double-stranded and is processed by Dicer in vitro. We further demonstrate the existence of small centromeric RNA in rdp1Δ cells. Our data suggest a pathway for siRNA generation that is distinct from the well-documented model involving RITS/RDRC. We propose that primary transcripts fold into hairpin-like structures that may be processed by Dcr1 into siRNAs, and that these siRNAs may initiate heterochromatin formation independent of RDRC activity. [ABSTRACT FROM AUTHOR]

Lymph node metastases (LNM) play a central role in the tumour–node–metastasis (TNM) classification for colorectal cancer (CRC), with extranodal extension (ENE) as an adverse feature. ENE has never been directly compared to tumour deposits (TD). The aim of this study was to perform an up‐to‐date systematic review, including a network meta‐analysis to compare their prognostic value. A comprehensive search was conducted on PubMed, Embase, Web of Science and Cochrane databases to identify all prognostic studies on ENE and TD. A total of 20 studies were included, with 7719 cases. The primary outcome was 5‐year disease‐free survival (DFS); secondary outcomes were overall survival (OS) and disease‐specific survival (DSS). Frequentist paired and network meta‐analyses were performed using the netmeta package in R. For univariable DFS analysis, LNM + TD+ cases had a significantly worse outcome compared with LNM + ENE+ cases [hazard ratio (HR) = 1.27, 95% confidence interval (CI) = 1.06–1.53], which was no longer significant for multivariable DFS analysis (HR = 1.13, 95% CI = 0.87–1.46). All OS and multivariable DSS analyses showed a significantly worse outcome for LNM + TD+ cases compared with LNM + ENE cases. For all outcomes, both LNM + TD+ and LNM + ENE+ had a significantly increased hazard compared with LNM+ cases. This study shows that there is a trend towards worse outcome for LNM + TD+ than LNM + ENE+, not statistically significant in multivariable DFS analysis. Both groups perform significantly worse than cases with LNM only. To improve the accuracy of CRC staging, we recommend to put more emphasis on both ENE and TD in the TNM classification, with the most prominent role for TD. [ABSTRACT FROM AUTHOR]