3）粘膜下囊胞由来の癌

Early Gastric Carcinoma Originating from Submucosal Heterotopia

要旨　粘膜下囊胞由来の胃癌はU・M領域に多く認められ，肉眼型はbridging foldを有するSMTを呈することが多い．また，SMT表面には中央部からやや偏位し，不整および発赤調を呈する陥凹所見を認め，自験例では粘液を排出する大小不同の乳頭状構造が観察される開口部が存在し，この大小不同の乳頭状構造が粘膜下囊胞由来の癌の診断において重要な所見と考えられた．癌の組織型は分化型管状腺癌が多く，深達度は粘膜下層にとどまり，リンパ節転移の頻度は低かった．EUSではhyper echoicなエコー輝度を中心にモザイクパターンを呈し，内部にはecho free spaceが散見されたが，囊胞内に癌の存在を示す所見とは考えられなかった．生検診断は癌組織が開口部に露呈している場合や粘膜筋板にまで進展する症例では可能であった．

　Most of gastric carcinomas derived from heterotopic gastric mucosa are located in the upper or middle portion of the stomach and reveal submucosal tumor-like lesions with bridging folds. The depression was recognized to deviated from the top of the tumor with an irregular margin or redness. In our case, the depression showed the orifice with an irregular papillary surface and a mucous secretion, so this finding was thought important to diagnose the carcinoma as arising from heterotopia. The histological type was mainly well differentiated tubular adenocarcinoma and the depth of carcinoma limited to the submucosal layer, with no lymph node metastasis. EUS findings showed a mosaic pattern with hyper echogenicity and echo-free space. However, this finding is not a characteristic for the to diagnose of carcinoma. In the definite diagnosis by biopsy specimens, we need to peep in mind that there is a low degree of accuracy in diagnosing this type of cancer.