胃内分泌細胞癌の内視鏡所見の特徴─胃内分泌腫瘍との比較から

Endoscopic Features of Gastric Neuroendocrine Carcinoma Compared with those of Neuroendocrine Tumor

要旨●胃のNEC（neuroendocrine carcinoma）は，発生頻度が胃癌全体の0.6％とまれだが，急速な発育性質を持ち，高い転移率の高悪性度腫瘍である．そのため進行した状態で診断されることが多く，確立された治療方法もないため予後不良の疾患である．また術前生検組織診断の正診率が低く，確定診断に時間を要することもある．診断率をよくするためには内視鏡所見を元に鑑別診断として挙げ，積極的に免疫染色を行うことが重要である．NECの報告例は少なく，系統的診断の一助とするために，当院で経験した消化管内分泌細胞腫瘍24例について，内視鏡的特徴を検討した．NET（neuroendocrine tumor）は，NECと比較して腫瘍径が小さく，発赤調または同色調の隆起型を呈し，表面に拡張した血管を認めることが多い．NECは進行癌が多く，肉眼型は大部分が2型であった．表在型の場合は0-IIc型や0-IIa＋IIc型といった陥凹性病変の占める割合が高く，病変辺縁部に粘膜下腫瘍様の立ち上がりを伴う症例が多かった．また表在型病変でも病理組織学的深達度は深く，リンパ節転移率も高かった．

　NEC（neuroendocrine carcinoma）of the stomach is a rare subtype of gastric cancer（0.6% of whole gastric cancer）. However, it has a high incidence of lymph node metastasis and frequently shows aggressive growth. Unfortunately, most lesions were diagnosed as an advanced cancer, and an effective treatment for those lesions has not been established yet. As a result, the prognosis of NEC is poor.

　The diagnostic accuracy using biopsy specimens was low. Therefore, immunohistochemical examinations should also be actively combined for early diagnosis. The neuroendocrine tumor was small in size compared with NEC and appeared as a reddish or similar colored elevated lesion. Dilated vessels were also frequently shown on the surface. The most common macroscopic type of NEC was type 2. Even if it showed a superficial type such as“0-IIc”or“0-IIc+IIa”, those were finally diagnosed as advanced cancer with lymph node metastasis.