悪性リンパ腫との鑑別が困難であった胃内分泌細胞癌の1例

Endocrine Cell Carcinoma of the Stomach, Report of a Case

要旨　症例は66歳の男性で，主訴はタール便である．胃X線および内視鏡検査で，胃体上部から前庭部の小彎側を中心に大きさ11×6cmの2型の腫瘍を認めた．腫瘍は部分的に粘膜下腫瘍様の形態を示し，胃壁の伸展性も保持されていた．生検組織像では，悪性リンパ腫との鑑別が困難であったが，免疫組織化学染色により胃内分泌細胞癌が示唆さたため胃全摘術を施行した．切除標本の病理組織所見では，N/C比が高く，核のクロマチン分布が均一な腫瘍細胞の増殖を認めた．標本内には明らかな腺癌成分は認められなかった．癌細胞の浸潤は漿膜に及んでおり，1群リンパ節に転移を認めた．免疫組織化学染色では，Grimelius，NSE，NCAM，chromogranin Aがいずれも陽性であり，胃原発の内分泌細胞癌と診断した．本例は，悪性リンパ腫との鑑別が画像診断上および病理組織学的にも困難であったが，免疫組織化学染色がその鑑別に有用であった．

　A 66-year-old man was admitted to Iwate Medical University hospital with the complaint of tarry stool. A gastric radiography, and an upper gastrointestinal endoscopic examination revealed a huge 2 type tumor in the lesser curvature of the stomach, which extended from the gastric upper body to the antrum. The tumor exhibited a submucosal tumor-like lesion, the gastric wall was well extended. It was difficult to determine from biopsy specimens from the gastric tumor whether the lesion was endocrine cell carcinoma or malignant lymphoma. Immunohistochemical stains led to suspicion of endocrine cell carcinoma. For this reason, total gastrectomy was performed. Histopathological findings showed homogeneous proliferation of neoplastic cells with a high N/C ratio and a fine chromatic nucleus, but adenocarcinoma was not observed. The neoplastic cells had invaded to the serosal layer and the metastatic lesion was diagnosed as confined to the D1 lymph node. Immunohistochemical stains showed the neoplastic cells had strong immunoreactivity with antibodies against Grimelius, NSE, NCAM and chromogranin A. This led us to a diagnosis of endocrine cell carcinoma of the stomach. In this paper, we reported the characteristics of images and histopathological findings of gastric endocrine cell carcinoma in this case. Gastric endocrine cell carcinoma has a characteristic of rapid growth and progression, and the prognosis is very poor. We cocluded that immunohistochemical stains were useful for diagnosis of gastric endocrine cell carcinoma.