早期胃癌における胃型分化型腺癌の肉眼的特徴とその臨床治療

Macroscopic Features of Differentiated Adenocarcinoma with Gastric or Intestinal Phenotype Expression in Early Gastric Cancer

要旨　外科的切除された早期胃癌351例について，組織型をpureな分化型，pureな未分化型，混在型と分類し，更に粘液形質の検討から胃型形質を示す腺癌（胃型腺癌）と腸型形質を示す腺癌（腸型腺癌）の肉眼的特徴を明らかにした．胃型分化型腺癌は腸型分化型腺癌に比し，分化型に未分化な組織型を含む混在型が多く，肉眼型は陥凹型，色調は正色調，その肉眼境界は不明瞭であった．組織学的に不明瞭な腫瘍境界部では，胃型粘液形質を有する腺窩上皮に類似した低異型度分化型腺癌が粘膜の表層から中層にかけて側方進展し，明らかな段差を形成しない傾向がみられた．一方，腸型腺癌は純粋な分化型腺癌で，肉眼型が隆起型，色調が発赤調，肉眼境界が明瞭で側方進展を伴わない傾向がみられた．以上の結果から，内視鏡的粘膜切除術（endoscopic mucosal resection; EMR）を行う際，胃型分化型腺癌はその浸潤範囲の正確な診断が必要で，かつ生検組織診断にあたっては胃型分化型腺癌の存在を常に念頭に置く必要がある．

　To clarify the macroscopic characteristics of differentiated adenocarcinoma with gastric or intestinal mucin phenotype, a total of 351 gastric surgical specimens were studied using the mucin histochemical and immunohistochemical method with gastric and small intestinal cell markers. The cases were divided into four mucin phenotypes ; adenocarcinomas with gastric mucin phenotype (17.7%), intestinal mucin phenotype (18.3%), combined mucin phenotype with both gastric and intestinal mucin (60.3%), and the type lacking in mucin (LOM, 3.7%).

　Macroscopically, a significant number of adenocarcinoma with gastric and combined mucin phenotype showed the depressed type, indistinct margin and monotonous tone of color in the mucosal layer, as compared to adenocarcinoma with intestinal mucin phenotype and LOM. On the other hand, adenocarcinoma with intestinal mucin phenotype macroscopically showed elevated type, distinct margin and red tone of color. Microscopically, differentiated adenocarcinoma with gastric or combined mucin phenotype, which showed low grade atypia similar to foveolar epithelium, were found to be spreading laterally in the superficial mucosal layer replacing normal foveolar epithelium. Macroscopically, they formed only shallow depression and a monotonous tone of color, so that a border line between cancerous and non-cancerous area could not be delineated. Moreover, in the primary mucosal layer they were likely to transform to undifferentiated adenocarcinoma in the deep mucosa or beyond the submucosal layer, while differentiated adenocarcinoma with intestinal mucin phenotype in the mucosa maintained almost the same histological type.