Evolving pathologic concepts of serrated lesions of the colorectum

Abstract

Serrated lesions and polyps of the colorectum include all nonmalignant epithelial neoplastic lesions showing serrated morphology in the crypt epithelium. Until recently, serrated colorectal lesions were largely classified into three categories: hyperplastic polyp (HP), sessile serrated adenoma/polyp (SSA/P), and traditional serrated adenoma (TSA). However, since the publication of the previous 2010 World Health Organization (WHO) classification, many studies have improved our knowledge of serrated colorectal lesion pathology. In the recently updated 2019 WHO classification, there have been important changes in classification, terminology, and diagnostic criteria for serrated colorectal lesions. In this review, we briefly summarize three major components of the pathology of serrated lesions: (1) updates on the 2019 WHO classification of serrated lesions, (2) updates on morphologic variants and dysplasia of serrated lesions, and (3) the molecular pathology of serrated lesions. UPDATES IN THE 2019 WHO CLASSIFICATION OF SERRATED COLORECTAL LESIONS Classification, terminology, and diagnostic criteria for serrated lesions/polyps of the colorectum are being revised, and their clinical implications and molecular features have also been newly discovered or modified. The WHO classification of tumors of the digestive system was recently updated to the 5th edition [1]. Compared to the previous edition, the 5th edition has demonstrated several notable changes in the section on serrated colorectal lesions/polyps. Changes in the terminology and categorization of serrated colorectal lesions There are major and minor changes in the terminology and categorization of serrated colorectal lesions. Alterations in the

NTRK oncogenic fusions are exclusively associated with the serrated neoplasia pathway in the colorectum and begin to occur in sessile serrated lesions

“…Thus, further validation studies are necessary to evaluate the potential utility of pan-TRK IHC positivity as an indicator of high-risk lesions among non-dysplastic SSLs. If pan-TRK IHC is determined to be helpful for selecting high-risk SSLs as other currently used risk factors such as morphological dysplasia, lesion size, and lesion multiplicity, 19, 36, 37 it will allow us to perform more precise surveillance and management of SSLs. Moreover, other IHC items that have been known to be useful for detecting oncogenic fusions, such as ALK IHC for ALK fusions, 38 may also be predictive factors for high-risk SSLs.…”

“…The 132 SSLs without morphological dysplasia were collected in our previous study, and the detailed histological criteria for the selection of SSLs were described in our previous reports. 18, 19 Other precursor lesions, including SSLDs, TSAs, HPs, CALGs, and CAHGs, were selected mainly based on the histological criteria of the latest WHO classification. 19, 20, 25, 26 This study was conducted in compliance with the ethical guidelines of the 2013 Declaration of Helsinki.…”

“…18, 19 Other precursor lesions, including SSLDs, TSAs, HPs, CALGs, and CAHGs, were selected mainly based on the histological criteria of the latest WHO classification. 19, 20, 25, 26 This study was conducted in compliance with the ethical guidelines of the 2013 Declaration of Helsinki. The Institutional Review Board (IRB) of SNUH approved this study (IRB No.…”

Endoscopic diagnosis for colorectal sessile serrated lesions

“…The pathological findings were evaluated by hematoxylin and eosin staining and histological diagnoses were made by an expert gastrointestinal pathologist (H. W.). Serrated lesions were classified as HP, SSL, and TSA according to the World Health Organization classification[ 16 , 17 ]. We collected data on polyps with endoscopic or pathological diagnosis of serrated polyps.…”

WNT5a in Colorectal Cancer: Research Progress and Challenges

“…Somatic methylation of the promoter of MLH1 causes majority of sporadic CRC with microsatellite instability (MSI) and the CpG island methylator phenotype (CIMP). 144 The CRC tumor with MSI often exhibited a favorable outcome, whereas the CRC tumor with CIMP shown a complex outcome associated with the status of MSI and BRAF V600E. BRAF V600E is a substitute marker of high CIMP and is a dependent prognostic factor of CRC tumor, which is associated with a poor outcome.…”