胃底腺型胃癌の1例

Gastric Adenocarcinoma of Fundic Grand Type, Report of a Case

要旨●患者は72歳，男性．市の胃がん内視鏡検診で胃穹窿部大彎前壁寄りに2cm大の発赤調隆起性病変を認めたため，精査・加療目的で当科へ紹介され受診となった．NBI（narrow band imaging）拡大観察では，表面構造・血管構造に癌を疑う所見は認められなかった．生検診断は高分化腺癌で，癌は粘膜層の中層から粘膜下層にかけて存在していた．切除標本では，主細胞に類似し，核異型性に富む細胞が不整な腺管を形成して，粘膜層の中層から粘膜下層を中心として増殖していた．腫瘍細胞は免疫組織学的にMUC6とpepsinogen Iに広範囲で陽性，H^＋/K^＋-ATPaseは一部で陽性であり，主細胞優位型の胃底腺型胃癌と診断した．Ki-67標識率は最大で30％と高値であった．癌として否定的な意見もある「胃底腺型胃癌」において，その存在を強く肯定する貴重な症例であると考えられた．

　Upper endoscopy screening in an asymptomatic 72-year-old man revealed a reddish elevated lesion 2cm in diameter on the anterior wall of the gastric cardia. He was referred to our hospital for further examination and treatment. Narrow band imaging showed no evidence of cancer in the surface structure and vasculature.

　Biopsy specimens from this lesion revealed a well-differentiated adenocarcinoma from the middle layer of the mucosa to submucosa. Histological analysis of the resected specimen revealed highly atypical cells similar to chief cells that formed an irregular gland mainly from the middle layer of the mucosa to submucosa. Immunohistologically, tumor cells were positive for MUC6, pepsinogen I, and partially positive for H＋/K＋-ATPase. We finally diagnosed this patient with gastric adenocarcinoma of the fundic gland type (chief cell predominant type）, with submucosal invasion. The Ki-67 index was as high as 32.8%. The existence of gastric adenocarcinoma of the fundic gland type is controversial ; however, this case appears to confirm it.