Pathological Diagnosis of Serrated Lesions and Their Outlook for the Future Tamotsu Sugai 1 , Makoto Eizuka 1 , Yoshihito Tanaka 1 1Division of Molecular Diagnostic Pathology, Department of Pathology, School of Medicine, Iwate Medical University, Morioka, Japan Keyword: 鋸歯状病変 , HP , TSA , SSA/P , MSI陽性大腸癌 pp.1491-1501
Published Date 2019/10/25
DOI https://doi.org/10.11477/mf.1403201861
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 Intramucosal colorectal neoplasia is classified into two subgroups:conventional and serrated. Although conventional neoplasia belongs to the types of cancers that arise from APC type, serrated neoplasia is subclassified as a BRAF/KRAS type of cancer. Whereas conventional type neoplasia is characterized by APC mutations/KRAS mutations, serrated neoplasia is closely associated with APC(−)/KRAS(+)mutations. In addition, BRAF mutations play an important role early in the development of serrated tumors. Thus TSA(traditional serrated adenoma)and SSA/P(sessile serrated adenoma/polyp) have different histopathological and molecular features. Histological characteristics of TSA include formation of villi at the surface, columnar cells with pencil-like nuclei and eosinophilic cytoplasm and budding(ectopic crypt foci). On the other hand, TSA is subclassified as a BRAF and KRAS type of cancer on the basis of histological differences in the polyp base. Histological diagnosis of SSA/P is based on the following criteria:(1)glandular dilatation, (2)asymmetric crypt branching, and(3)crypt dilatation or abnormal arrangement of the crypt base. Molecular alterations are characterized by BRAF mutations and CpG island methylator phenotype-high status. Molecular alteration is correlated with the third of the three criteria for SSA/P diagnosis. For pathological diagnosis of SSA/P with cytological dysplasia, it is useful to examine immunostaining of mutant anti-BRAF antibody and MLH1/PMS2 proteins. Several variants of serrate lesions, including superficial serrated adenoma, mucin-rich TSA, and serrated tubulovillous adenoma, have been reported. Such lesions must be examined further to establish the pathological entity. We suggest that the molecular alterations enable the pathological diagnosis of serrated lesions.

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