胃底腺ポリープ関連腫瘍（胃底腺粘膜型腺癌）の1例

Adenocarcinoma with a Gastric Mucin Phenotype Arising from a Fundic Gland Polyp in a Patient with Familial Adenomatous Polyposis, Report of a Case

要旨●患者は30歳代，女性．FAPに対する大腸全摘後で5年前に早期胃癌に対しESDを行い，その後も定期的にEGDを施行していた．通常観察にて多発する胃底腺ポリープに比べ発赤調を呈する7mm大の隆起を胃体中部大彎に認め，生検にてGroup 5（tub1）とした．NBI拡大観察では胃底腺ポリープを反映する規則正しい類円形pit領域と境界を有し，口側には密度の高いpit様構造，中央には不整な顆粒・鱗状構造を認め，Endocyotoscopyでは構造の不整と軽度腫大した核の所見を認めた．ESD切除標本の病理組織像では異型腺窩上皮だけでなく，その周囲の胃底腺にも軽度の核異型，構造異型，MUC5AC染色陽性による分化の異常，Ki-67増殖活性高値を認めたことより腫瘍であると考え，胃底腺ポリープ内に発生した胃底腺粘膜型腺癌と診断した．腺窩上皮領域の異型のみでなく，近傍の胃底腺領域にも異型を認めた極めてまれな症例と考えられた．

　A female in her 20s with familial adenomatous polyposis after total colectomy underwent endoscopy as part of her annual cancer surveillance. An endoscopic examination revealed a 7mm elevated lesion that was slightly reddish compared to the nearby fundic gland polyps. The biopsy specimens of the lesion revealed well- differentiated adenocarcinoma, therefore ESD（endoscopic submucosal dissection）was recommended. Magnifying narrow band imaging revealed an irregular microsurface pattern in areas with regular round pits, indicating a fundic gland polyp, and endocytoscopy revealed irregular glands with slight nuclear swelling, so we performed ESD on this lesion. This tumor was diagnosed histopathologically as adenocarcinoma（tub1, low）, Type 0-I, pT1a（M）, Ly0, V0, pHM0, pVM0, particularly gastric adenocarcinoma of fundic gland mucosa type based foveolar epithelial atypia and fundic gland dysplasia examined by immunohistochemical staining. It was a rare case in which a variant in not only dysplasia of the foveolar epithelium but also dysplasia of the fundic gland was recognized.