未分化型混在早期胃癌の病理学的特徴と問題点―分子病理学的特徴

Molecular Characteristics of Mixed type Adenocarcinoma of the Stomach

要旨　胃型形質をもつ分化型腺癌は未分化型へ脱分化することが知られている．このことから混在癌は分化型に由来すると考えられてきたが，E-cadherin/catenin complexの変化，p53の遺伝子異常，CGHによる系譜解析の結果からみると，混在癌には分化型に由来するもの以外に未分化型に由来するものもあることがわかった．この両者は粘膜内に印環細胞へ分化する層構造がみられるかどうかによって識別できる可能性がある．混在癌の治療方針を策定する際にも，この由来の違いを考慮することが必要である．

　It has been reported that undifferentiated type gastric carcinoma derives partially from differentiated type gastric carcinoma with gastric phenotype. This process of dedifferentiation may form a mixed differentiated and undifferentiated type. However, the data of cytogenetic profile, genetic abnormalities of TP53 and alterations of E-cadherin/catenin complex support the notion that a mixed type can derive from the undifferentiated type as well as from the differentiated type. The former and the latter are characterized by the presence and absence, respectively, of intramucosal signet ring cells that differentiate regularly in a layered structure. The difference of derivation should be taken into consideration in clinical evaluation of a mixed type adenocarcinoma for therapeutic interventions.