[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.