WHO分類 第6版における大腸sessile serrated lesion with dysplasia（SSLD）の病理診断—本邦病理診断との対応を含めて

Pathological Diagnosis of Colorectal Sessile Serrated Lesion with Dysplasia（SSLD） in the WHO Classification, 6th Edition, and Its Correspondence with Japanese Diagnostic Criteria

要旨●大腸癌において鋸歯状経路は主要な発癌経路の一つであり，その初期病変である広基性鋸歯状病変（SSL）およびSSLD（SSL with dysplasia）の理解は重要である．本稿ではWHO分類 第6版に基づき，SSL/SSLDの概念と診断基準を概説した．特にSSLDの位置付け，dysplasia成分の組織学的多様性，TSAとの関係，MLH1・p53・BRAF免疫染色の意義について触れ，さらに本邦における大腸腫瘍病理診断基準との対応関係を示しながら日常診断における問題点を考察した．

　Serrated pathway is recognized as one of the major carcinogenic pathways in colorectal cancer, and understanding the early lesions within this pathway, including sessile serrated lesions（SSLs）and SSLs with dysplasia（SSLDs）, is essential. In this review, we summarize the diagnostic criteria of SSLs/SSLDs based on the World Health Organization（WHO）Classification of Tumors, 6th edition, and discuss issues in routine diagnostic practice. We particularly focused on the classification of SSLDs, the wide histologic spectrum of dysplastic components, their relationship with traditional serrated adenomas, and the diagnostic significance of immunohistochemistry. In addition, we compared the WHO classification with the Japanese pathological diagnostic criteria for colorectal neoplasms.