大きな粘膜下腫瘍様の形態を呈したHelicobacter pylori陰性未分化型胃癌の1例

A Large Submucosal Tumor-like Undifferentiated Type Gastric Cancer without Helicobacter pylori Infection, Report of a Case

要旨●患者は40歳代，女性．健診にて軽度の貧血を指摘され，前医にて上部消化管内視鏡検査を受けたところ，胃前庭部後壁に粘膜下腫瘍様の隆起性病変を指摘された．半球状の形態を呈し，病変中心に潰瘍を形成していた．生検にて印環細胞癌が検出され，20XX年10月に精査加療目的で当院へ紹介された．拡大内視鏡所見では，隆起の表面は大部分が非腫瘍粘膜に覆われていたが，病変中心部の潰瘍辺縁とその近傍の小びらんには血管の口径不同を認めた．超音波内視鏡検査では，辺縁不明瞭なびまん性の壁肥厚を呈していた．背景粘膜に萎縮はなく，Helicobacter pylori未感染と考えられた．幽門側胃切除術を施行し，病理組織学的には未分化型腺癌が粘膜内から漿膜下まで浸潤し，静脈侵襲を認めたが，リンパ管侵襲やリンパ節転移はみられなかった．

　A woman in her 40s was referred to the Nagano Red Cross Hospital in October 2015 for further examination and treatment of gastric cancer. She had been diagnosed to be slightly anemic during a medical checkup and had undergone EGD（esophagogastroduodenoscopy）at another hospital. EGD revealed a large submucosal tumor-like protruded lesion with irregular-shaped ulcers and a small erosion in the posterior of the antrum ; biopsy specimens of the lesion showed signet ring cell carcinoma. When she visited our hospital, she had no complaints, and physical examination revealed no abnormal findings. EGD using a magnifying endoscope with narrow-band imaging showed an irregular microvascular pattern at the surface of the small erosion and suggested an undifferentiated adenocarcinoma in the subepithelial portion. No atrophic changes were observed in the background of the lesion. The rapid urease test and serological tests for Helicobacter pylori antibodies were negative. Endoscopic ultrasonography revealed diffuse wall thickening and disappearing of wall layer. Computed tomography showed no metastasis in the liver and lung. Distal gastrectomy was performed in November 2015. Histopathologically, the tumor was diagnosed as a poorly differentiated adenocarcinoma extending from the mucosal layer to the subserosal layer without metastasis into the lymph nodes.