Curriculum review: serrated lesions of the colorectum

The histologic features, molecular features, detection and management of serrated polyps: a review

The serrated pathway to colorectal cancers (CRCs) is a significant pathway encompassing five distinct types of lesions, namely hyperplastic polyps (HPs), sessile serrated lesions (SSLs), sessile serrated lesions with dysplasia (SSL-Ds), traditional serrated adenomas (TSAs), and serrated adenoma unclassified. In contrast to the conventional adenoma-carcinoma pathway, the serrated pathway primarily involves two mechanisms: BRAF/KRAS mutations and CpG island methylator phenotype (CIMP). HPs are the most prevalent non-malignant lesions, while SSLs play a crucial role as precursors to CRCs, On the other hand, traditional serrated adenomas (TSAs) are the least frequently encountered subtype, also serving as precursors to CRCs. It is crucial to differentiate these lesions based on their unique morphological characteristics observed in histology and colonoscopy, as the identification and management of these serrated lesions significantly impact colorectal cancer screening programs. The management of these lesions necessitates the crucial steps of removing premalignant lesions and implementing regular surveillance. This article provides a comprehensive summary of the epidemiology, histologic features, molecular features, and detection methods for various serrated polyps, along with recommendations for their management and surveillance.

Single-cell landscape of the cellular microenvironment in three different colonic polyp subtypes in children

BACKGROUND

The understanding of the heterogeneous cellular microenvironment of colonic polyps in paediatric patients with solitary juvenile polyps (SJPs), polyposis syndrome (PJS) and Peutz-Jeghers syndrome (PJS) remains limited.

METHODS

We conducted single-cell RNA sequencing and multiplexed immunohistochemistry (mIHC) analyses on both normal colonic tissue and different types of colonic polyps obtained from paediatric patients.

RESULTS

We identified both shared and disease-specific cell subsets and expression patterns that played important roles in shaping the unique cellular microenvironments observed in each polyp subtype. As such, increased myeloid, endothelial and epithelial cells were the most prominent features of SJP, JPS and PJS polyps, respectively. Noticeably, memory B cells were increased, and a cluster of epithelial-mesenchymal transition (EMT)-like colonocytes existed across all polyp subtypes. Abundant neutrophil infiltration was observed in SJP polyps, while CX3CR1hi CD8+ T cells and regulatory T cells (Tregs) were predominant in SJP and JPS polyps, while GZMAhi natural killer T cells were predominant in PJS polyps. Compared with normal colonic tissues, myeloid cells exhibited specific induction of genes involved in chemotaxis and interferon-related pathways in SJP polyps, whereas fibroblasts in JPS polyps had upregulation of myofiber-associated genes and epithelial cells in PJS polyps exhibited induction of a series of nutrient absorption-related genes. In addition, the TNF-α response was uniformly upregulated in most cell subsets across all polyp subtypes, while endothelial cells and fibroblasts separately showed upregulated cell adhesion and EMT signalling in SJP and JPS polyps. Cell-cell interaction network analysis showed markedly enhanced intercellular communication, such as TNF, VEGF, CXCL and collagen signalling networks, among most cell subsets in polyps, especially SJP and JPS polyps.

CONCLUSION

These findings strengthen our understanding of the heterogeneous cellular microenvironment of polyp subtypes and identify potential therapeutic approaches to reduce the recurrence of polyps in children.

WHICH LESIONS ARE AT HIGHER RISK OF DEVELOPING COLORECTAL CARCINOMAS: SUPERFICIALLY ELEVATED SERRATED LESIONS OR DEPRESSED LESIONS?

BACKGROUND

There are lesions that are still being missed in colonoscopy. Many of those could be superficially elevated serrated lesions or depressed ones.

AIMS

The aim of this study was to compare the histopathological characteristics of these lesions and their risks for submucosal carcinoma.

METHODS

This is a retrospective, cross-sectional, and observational study comparing 217 superficially elevated serrated lesions larger than 5 mm resected by colonoscopies (G1) with 558 depressed lesions (G2).

RESULTS

In G1, 217 lesions were found in 12,653 (1.7%) colonoscopies; in G2, 558 lesions were found in 36,174 (1.5%) colonoscopies. In G1, 63.4% were women and in G2, there was no gender predominance. The average size of G1 was 16.2 mm and G2 was 9.2 mm (p<0.001). G1 predominated on the proximal colon and G2 on the distal and rectum (p<0.001). In G1, there were 214 (98.6%) low-grade intramucosal neoplasia and 3 (1.4%) high-grade intramucosal neoplasia. Excluding 126 hyperplastic polyps and considering 91 sessile serrated adenomas in G1, we observed 88 (96.7%) low-grade intramucosal neoplasia and 3 (3.3%) high-grade intramucosal neoplasia; in G2, we observed 417 (74.7%) low-grade intramucosal neoplasia, 113 (20.3%) high-grade intramucosal neoplasia, and 28 (5.0%) submucosal adenocarcinomas (p<0.001).

CONCLUSION

Depressed lesions significantly had more high-grade intramucosal neoplasia and more invasive carcinomas in the submucosal layer than superficially elevated serrated lesions and more than superficially elevated sessile serrated adenomas.

N6-methyladenosine methyltransferase KIAA1429 elevates colorectal cancer aerobic glycolysis via HK2-dependent manner

Emerging evidence has emphasized the critical roles played by N⁶-methyladenosine RNA (m⁶A) modification in colorectal carcinoma (CRC) initiation and progression. However, the roles and mechanism of m⁶A and KIAA1429 in CRC progression require further clarification. Here, our research aimed to investigate the functions of KIAA1429 in CRC tumorigenesis. Results indicated that KIAA1429 up-regulation closely correlated to the poor prognosis of CRC patients. Bio-functional assays demonstrated that KIAA1429 promoted the aerobic glycolysis, including glucose uptake, lactate production, ATP generation and extracellular acidification rate (ECAR). Mechanistically, KIAA1429 positively up-regulated HK2 level via increasing its mRNA stability by binding the m⁶A site of HK2 mRNA via m⁶A-independent manner. Collectively, our work indicates that KIAA1429 has the potential to promote CRC carcinogenesis by targeting HK2 via m⁶A-independent manner, providing insight into the critical roles of m⁶A in CRC.

TXI (Texture and Color Enhancement Imaging) for Serrated Colorectal Lesions

BACKGROUND AND AIM

Olympus Corporation released the texture and color enhancement imaging (TXI) technology as a novel image-enhancing endoscopic technique. We investigated the effectiveness of TXI in the imaging of serrated colorectal polyps, including sessile serrated lesions (SSLs).

METHODS

Serrated colorectal polyps were observed using white light imaging (WLI), TXI, narrow-band imaging (NBI), and chromoendoscopy with and without magnification. Serrated polyps were histologically confirmed. TXI was compared with WLI, NBI, and chromoendoscopy for the visibility of the lesions without magnification and for that of the vessel and surface patterns with magnification. Three expert endoscopists evaluated the visibility scores, which were classified from 1 to 4.

RESULTS

Twenty-nine consecutive serrated polyps were evaluated. In the visibility score without magnification, TXI was significantly superior to WLI but inferior to chromoendoscopy in the imaging of serrated polyps and the sub-analysis of SSLs. In the visibility score for vessel patterns with magnification, TXI was significantly superior to WLI and chromoendoscopy in the imaging of serrated polyps and the sub-analysis of SSLs. In the visibility score for surface patterns with magnification, TXI was significantly superior to WLI but inferior to NBI in serrated polyps and in the sub-analysis of SSLs and hyperplastic polyps.

CONCLUSIONS

TXI provided higher visibility than did WLI for serrated, colorectal polyps, including SSLs.