急速に発育した胃神経内分泌癌（NEC）における内視鏡所見の遡及的検討

Endoscopic Findings in Rapidly Growing Gastric Neuroendocrine Carcinoma（NEC）：A Case Report

要旨●患者は70歳代，男性．早期胃癌内視鏡治療後のサーベイランス検査で，胃前庭部後壁の治療瘢痕に接する部位に深い潰瘍（delle）を伴う径20mm超の上皮下腫瘍を認めた．生検では異型の強い腫瘍細胞の充実性胞巣を認め，病理組織学的所見と免疫組織化学染色のAE1/AE3およびシナプトフィジンが陽性で，Ki-67 index 20%以上（80%）を示したことから胃神経内分泌癌（NEC）と診断した．腹部造影CTとEOB-MRI検査で多発リンパ節転移に加えて肝転移が指摘され，化学療法が選択された．本症例は発見前年まで胃NECの発生を示唆する特異的な粘膜変化を認識できなかった．筆者らは，急速な発育過程や病理組織学的所見および免疫組織化学的所見より，（いわゆる）pure NECと推測した．

　Herein, we present the case of a male patient in his 70s in whom a submucosal tumor of approximately 20mm in diameter was found adjacent to the ESD（endoscopic submucosal dissection）scar in the posterior wall of the gastric antrum. This tumor was detected 11 years after early gastric cancer ESD during a surveillance upper gastrointestinal endoscopy. A deep ulcer（delle）was found at the summit of the elevation. Biopsy specimens indicated a densely packed nest of tumor cells with high atypia. Immunostaining for AE1/AE3 and synaptophysin revealed positive results, with the Ki-67 index exceeding 20%. These findings indicated a histological diagnosis of gastric NEC（neuroendocrine carcinoma）. Abdominal contrast-enhanced computed tomography and gadoxetic acid-enhanced magnetic resonance imaging examination indicated multiple lymph node and liver metastases, prompting chemotherapy as the treatment of choice. The specific mucosal changes indicating gastric NEC occurrence could not be recognized until a year before its detection. It may have originated as a subepithelial lesion and rapidly progressed into a so-called pure NEC, emphasizing the difficulty in capturing its initial image.