大腸上皮性腫瘍における粘液形質発現の意義

Significance of Phenotypic Expression in Colorectal Epithelial Tumors

要旨　大腸癌は，胃腺窩上皮（MUC5AC/HGM），腸杯細胞（MUC2），小腸刷子縁（CD10）に対するマーカーを用いて大腸型，小腸型，胃型，混合型，分類不能型に分類可能である．そして，小腸型は高悪性度（静脈浸潤・肝転移が高頻度），大腸型は比較的低悪性度，混合型は粘液癌・絨毛腫瘍由来の癌・腸炎関連癌に高頻度，胃型は高度の浸潤性や低分化傾向を示し鋸歯状病変との関連のある癌，などの特徴があり，形質発現は組織像と対応して生物学的態度とも関連している．また，大腸腺腫においては組織型（管状，絨毛，鋸歯状）の違いにより形質発現は異なる．さらに管状腺腫においては隆起型と非隆起型でも異なる傾向があり，非隆起型管状腺腫は高率にCD10を発現することにより，高悪性度小腸型形質癌の前駆病変として注目すべきである．このように大腸上皮性腫瘍において，粘液形質発現の解析が今後の研究に応用されることが期待される．

　Colorectal carcinomas can be classified into colonic type, small intestine type, gastric type, mixed type and unclassified type, according to the combination of expression of three markers ; MUC5AC/HGM for gastric foveolar cells ; the intestinal cup cell MUC2 for intestinal goblet cells and CD10 for the small intestinal brush border. As for the small intestine type, it has high-grade malignancy with high frequency of venous invasion and liver metastasis. As for the colon type, it has relatively low-grade malignancy. As for the mixed type, mucinous carcinoma, villous carcinoma and colitic carcinoma are included. As for gastric type, it is related to serrated carcinoma with prominent infiltrative growth and a tendency of dedifferentiation.

　In addition, phenotypic expression varies according to the difference of histological types（tubular, villous, serrated）in colorectal adenomas. Furthermore, even in the tubular type there is a difference in phenotypic expression between polypoid and non-polypoid types. Non-polypoid tubular adenoma tended to express CD10 and should be attended to as a precursor lesion of CD10 positive carcinoma with high-grade malignancy.

　In this way, the phenotypic expression is closely related to histological features and biological behaviors. It is expected that analysis of phenotypic expression will be applied in future investigation of colorectal carcinomas.