Ⅱa＋Ⅱc型早期胃癌の内視鏡診断

Endoscopic Diagnosis of Ⅱa+Ⅱc Type Early Gastric Cancer

　早期胃癌の詳細な解析が各方面から行なわれているが，Ⅱa＋Ⅱc型早期胃癌に関しては文献が大変少ないのに驚くほどである．この型の内視鏡診断は余り問題がないのかもしれない．

　しかし，臨床上重要な問題が1つある．すなわち，Ⅱa＋Ⅱc型は進展が比較的早く，肝転移をおこしやすく，予後も早期胃癌の中では最も悪いと考えられている．この型のほとんどは粘膜下に癌浸潤を伴って発見される．一般にⅡa＋Ⅱc型のⅡa部は癌の粘膜下浸潤のために生じたものである．したがって，より早期の発見が必要であり，そのための逆行的追跡も極めて重要な仕事である．そういう作業から発見されたビラン，または極めてわずかな陥凹を生検することも大切である．いわゆるタコイボ型胃炎のビランと全く外観上の区別がつかぬこともあるので注意を要する¹⁾．Ⅱa＋Ⅱc型早期胃癌が，より早期にどんな内視鏡像を呈しているかを未だ不十分な資料ではあるが，若干の検討を加えてみたい．

　Early gastric cancer of Ⅱa+Ⅱc type requires earliest possible detection not only because it is biologically very malignant but also because its incidence in metastases to the liver and lymph nodes is very high.

　Based on the histopathological findings, Sano has classified this variety into three groups: polypous, erosive and deep penetrating. Their endoscopic characteristics are as follows:- 　In the polypous type, its Ⅱa part is mostly seen as an open circle or as a cluster of small lesions. White coat over the Ⅱc portion is slight, if at all. This makes it difficult to differentiate it from Ⅱa type early cancer, Erosive type displays no definite characteristics. Even though white coat is often observed over it, discrimination from Ⅱa is mostly difficult. Most typical findings of Ⅱa+Ⅱc type are presented by the deep penetrating type. It is seen either as a whole circle or open circle, sometimes accompanied with mucosal convergency, so that it is liable to be mistaken for an advanced carcinoma. Thick white coat is invariably seen over it. This type always involves the submucosa.

　A Ⅱa+Ⅱc type lesion 1 to 2 cm in dimensions eventually needs biopsy for its confirmation and that 2 to 4 cm in diameter calls for differentiation from advanced carcinoma. Generally speaking, mucosal overhang around the ulcer in advanced carcinoma is over the usual height of a Ⅱa early cancer. A Ⅱa+Ⅱc lesion more than 4 cm in diameter should be considered advanced cancer.

　In retrospective follow-up studies of Ⅱa+Ⅱc early gastric cancer, its earlier stage is said to consists of small Ⅱ a lesions. More earlier still, minute Ⅱa or Ⅱb is reported to account for the initial stage of Ⅱa+Ⅱc early cancer. At present, further confirmation is required.