大腸鋸歯状腺腫の組織発生

Histogenesis of Serrated Adenoma

要旨　鋸歯状腺腫は正常大腸腺管構造を模倣した腫瘍であることを以前報告した．形態学的に2種類の腫瘍細胞が鋸歯状腺腫にはみられ，1つは正常腺管表層部に類似する終末分化細胞で，他の1つは正常腺管下層部に類似する腺管下層部細胞である．正常腺管上層部と下層部で特異的に発現する蛋白が，終末分化細胞と腺管下層部細胞にも同じように発現するか免疫染色で調べた結果，鋸歯状腺腫の終末分化細胞は正常腺管上層部と，腺管下層細胞は正常腺管下層部と同じ発現を示した．終末分化の異常発現という概念を導入することにより，過形成性ポリープや鋸歯状腺腫また管状腺腫との関係が一元的に説明可能であることを示した．鋸歯状腺腫は2種類の細胞が組み合わさって独特の形態を示す腺腫で，増殖と分化の解析の良いモデルとなる病変である．

　We reported previously that serrated adenoma has a structure mimicking normal colonic crypt. Two types of tumor cells were morphologically found in a serrated adenoma ; one is terminally differentiated cells which have the characteristics of the superficial epithelium of the normal crypt and the other is lower crypt cells which were similar to columnar cells of normal lower crypt. Immunohistochemical study disclosed that terminally differentiated cells and lower crypt cells of serrated adenoma show the same staining results of superficial epithelium and lower crypt columnar cells, respectively. The concept of "terminal differentiation" may be able to explain comprehensively the intimate relationsships between three colorectal lesions ; serrated adenoma, hyperplastic polyp and tubular adenoma. The latter two lesions are considered to be antecedent lesions of the former one. Serrated adenoma may be considered to be a good model to investigate the molecular aspects of proliferation and differentiation of colonic epithelial cells.