[Coexpression of CD44 and Ki-67 in colon`s neoplast]

[A new one in the classification of benign colon epithelial tumors (WHO, 2019, 5th edition)]

The 2019 WHO Classification of Benign Colon Epithelial Neoplasms includes serrated dysplasia, adenomatous polyps, and glandular intraepithelial neoplasia. Serrated dysplasia (ICD-O 8213/0 and 8213/2) is former serrated masses. There is an expected change in its terminology: it is proposed to use the term 'sessile serrated lesion' (SSL) instead of that 'sessile serrated polyp/adenoma' that causes a lot of discussion. The 2019 WHO Classification versus the 2010 WHO classification more clearly defines the TSA criteria: slit-like serration and high elongated cells with pronounced eosinophilic cytoplasm and an elongated pencillate nucleus. The traditional adenomas are renamed in the classification; the term 'adenomatous polyps' that still includes tubular, tubulovillous, and villous adenomas is adopted instead of the term 'adenomas'. The criteria for adenomas remain the same (by the area occupied by villous structures). The 5th edition introduces a separate large section devoted to inflammatory bowel disease-associated dysplasia that is defined as obvious epithelial neoplastic changes that are limited to the basement membrane. The diagnosis can only be used for specific lesions, such as Crohn's colitis and ulcerative colitis.

Terminology, Molecular Features, Epidemiology, and Management of Serrated Colorectal Neoplasia

In addition to the adenoma to carcinoma sequence, colorectal carcinogenesis can occur via the serrated pathway. Studies have focused on clarification of categories and molecular features of serrated polyps, as well as endoscopic detection and risk assessment. Guidelines from the World Health Organization propose assigning serrated polyps to categories of hyperplastic polyps, traditional serrated adenomas, and sessile serrated lesions (SSLs). Traditional serrated adenomas and SSLs are precursors to colorectal cancer. The serrated pathway is characterized by mutations in RAS and RAF, disruptions to the Wnt signaling pathway, and widespread methylation of CpG islands. Epidemiology studies of serrated polyps have been hampered by inconsistencies in terminology and reporting, but the prevalence of serrated class polyps is 20%-40% in average-risk individuals; most serrated polyps detected are hyperplastic. SSLs, the most common premalignant serrated subtype, and are found in up to 15% of average-risk patients by high-detecting endoscopists. Variations in rate of endoscopic detection of serrated polyps indicate the need for careful examination, with adequate bowel preparation and sufficient withdrawal times. Risk factors for SSLs include white race, family history of colorectal cancer, smoking, and alcohol intake. Patients with serrated polyps, particularly SSLs and traditional serrated adenomas, have an increased risk of synchronous and metachronous advanced neoplasia. Surveillance guidelines vary among countries, but SSLs and proximal hyperplastic polyps require special attention in assignment of surveillance interval-especially in light of concerns regarding incomplete detection and resection.