粘膜下腫瘍様の形態を呈した大きさ15mm大の胃内分泌細胞癌の1例

Endocrine Cell Carcinoma of Stomach Mimicking Submucosal Tumor, Report of a Case

要旨　患者は48歳，男性．主訴は心窩部痛．胃X線および内視鏡検査で，前庭部小彎に大きさ約15mm大でbridging holdを伴う粘膜下腫瘍様の隆起性病変を認めた．また，隆起の頂部には大きさ約7mm大の不整陥凹を認めた．同部位からの生検で低分化腺癌の診断を得たため，粘膜下層以深に深部浸潤した胃癌と診断し，手術を施行した．病理組織学的には陥凹部の粘膜面の一部に高分化型腺癌を認めたが，腫瘍の主座は粘膜下層にあり，肺の小細胞癌類似の小型の異型細胞が充実性に増殖し，漿膜下層まで浸潤していた．Grimelius染色は陰性であったが免疫染色のchromogranin Aが陽性を示し，また一部にロゼット様構造を認め，胃内分泌細胞癌と最終診断した．胃内分泌細胞癌は，発育進展速度が速く予後不良と考えられている比較的頻度の少ない腫瘍である．今回は画像所見および病理組織学的特徴を中心に報告した．

　The patient was a 48-year-old man. His main compliant was epigastralgia. X-ray and endoscopy of the stomach revealed a protuberant lesion in the lesser curvature, approximately 15 mm in size (diameter), with bridging fold appearance at the top. As biopsy revealed that it was a poorly differentiated adenocarcinoma, an operation was performed under the diagnosis of stomach cancer infiltrating further than the submucosa. Histopathologically, a part of the mucosa at the dent was a highly differentiated adenocarcinoma, but the tumor focus was in the submucosa, where small-size atypical cells, closely resembling those of small cell carcinoma of the lung, proliferated vigprously, infiltrating the subserosa. The lesion was negative for Grimelius staining but positive for the immunostaining of chromogranin A. Rosette-like formation was partially observed. The lesion was finally diagnosed as endocrine cell carcinoma of the stomach. Endocrine cell carcinoma of the stomach is a relatively rare tumor which grows and progresses rapidly and its prognosis is thought to be poor. We focused on the image findings and histopathological characteristics of the lesion in this study.