症例 特異な形態を呈した巨大な幽門腺腺腫由来の胃腸混合型粘膜内胃癌の１例

症例は80歳代女性．上部消化管内視鏡検査で，噴門部直下に丈の高い乳頭状隆起と周囲に裾野を広げるような平坦隆起を伴った巨大な腫瘍を認めた．幽門腺腺腫と考えられたが，担癌の可能性が否定できないため外科的切除を選択した．病理組織学的には，隆起部分は幽門腺腺腫の領域と乳頭管状構築を示す胃腸混合型の高分化型腺癌から構成されていた．丈の低い領域は，表層は腺窩上皮に，中層付近は幽門腺・粘液細胞への分化を示す幽門腺腺腫であった．以上より，幽門腺腺腫から発生した高分化型腺癌と診断した．幽門腺腺腫から発生した胃腸混合型腺癌の報告は少なく，また，本例は特異な肉眼形態を呈しており貴重な症例と考えられた．

An 80-year-old woman presented for further evaluation of a huge gastric tumor. Esophagogastroduodenoscopy revealed a huge tumor at the gastric fundus and upper body. The tumor appeared as a protruding papillary mass surrounded by a flat elevated lesion. Based on the endoscopic findings, we diagnosed the lesion as a pyloric gland adenoma; however, we suspected that the protruding lesion included a concurrent carcinomatous component and therefore performed laparoscopic total gastrectomy. Histopathological evaluation of the protruding lesion showed findings of a pyloric gland adenoma and well-differentiated adenocarcinoma. The adenocarcinoma component showed papillary morphology combined with gastric and intestinal mucin phenotype. The surface layer of the flat elevated lesion showed tumor cell differentiation into foveolar epithelium, and the middle layer showed cells that were differentiated into pyloric glands. We diagnosed the tumor as an adenocarcinoma that originated from a pyloric gland adenoma. We report a rare case of an adenocarcinoma of combined with gastric and intestinal mucin phenotype that originated from a huge pyloric gland adenoma.