胃神経内分泌腫瘍（NEN）の内視鏡診断からみた治療方針

Endoscopic Diagnosis and Clinical Management of Gastric Neuroendocrine Neoplasm（NEN）

要旨●胃神経内分泌腫瘍（neuroendocrine neoplasm ; NEN）は，高分化の胃NET（neuroendocrine tumor）と低分化の胃NEC（neuroendocrine carcinoma）に大別される．胃NETは内分泌前駆細胞から発生した細胞異型度の低い低悪性度の腫瘍で，悪性度の高い胃NECと起源・生物学的性質が異なる腫瘍である．胃NETの内視鏡像は表在型で，発赤調または正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く，その形態はSMT様隆起，たこいぼ状隆起，発赤ポリープ様に分けられた．胃NETの治療方針決定には①背景粘膜の内視鏡所見やガストリン値をもとにした病因（Rindi分類）の評価，②EUSを用いた腫瘍径と壁深達度の評価，③生検によるgradeの評価が重要で，1cm未満の少数のType 1 NETには内視鏡治療が，Type 3 NETには基本的に外科手術が推奨されている．治療方針については強固なエビデンスが少ないことから各ガイドラインの推奨に若干の不一致があり，個々の症例に応じて多職種間討議も踏まえた方針の決定が重要と考えられた．胃NECは予後が不良で集学的治療が適応となる．

　Gastric NEN（neuroendocrine neoplasm）is categorized into well differentiated NET（neuroendocrine tumor）and poorly differentiated NEC（neuroendocrine carcinoma）. NETs are low-grade tumors with low cellular atypia arising from endocrine progenitor cells, and are distinct in origin and biology from high-grade gastric NETs. The endoscopic picture of gastric NETs is superficial, with erythematous or orthochromatic elevations, often with dilated vessels on the surface, and the morphology was divided into SMT-like elevations, tako-villus-like elevations, and erythematous polyp-like elevations. In determining the treatment strategy for gastric NETs, （1） evaluation of etiology（Rindi classification）based on endoscopic findings of the background mucosa and gastrin levels, （2） evaluation of tumor diameter and wall depth using EUS, and（3） evaluation of grade by biopsy are important, and endoscopic treatment is recommended for a few Type 1 NETs smaller than 1cm, while surgery is basically recommended for Type 3 NETs. Surgery is basically recommended for Type 3 NETs. There was some discrepancy in the recommendations of each guideline for treatment policy due to the lack of solid evidence, and it was considered important to determine a policy based on multidisciplinary discussions according to each case. Gastric NEC required multimodal management because of its highly aggressive biological behavior.