H. pylori陰性胃底腺粘膜に発生した胃型腺腫由来の低異型度高分化腺癌の1例

Low-grade, Well-differentiated Adenocarcinoma Arising in Gastric-type Adenoma in a Helicobacter pylori-Negative Patient, Report of a Case

要旨●患者は60歳代，男性．H. pylori未感染．前医で施行した上部消化管内視鏡検査（EGD）で胃癌が疑われ，精査加療目的に当科へ紹介となった．治療前のEGDで胃穹窿部に平坦隆起性病変を認めた．白色光観察では病変は淡い発赤調，強い発赤調，白色調の3領域から構成されていた．拡大観察では強い発赤調領域に一致して微小血管の口径不同を認め高分化腺癌を疑い，内視鏡治療の方針とした．切除標本の病理組織学的検索では，淡い発赤調領域はMUC6陽性細胞が主体の胃型（幽門腺型）腺腫から成り，強い発赤調領域にはMUC6とMUC5AC陽性細胞が混在する胃型形質を示す低異型度高分化腺癌成分を認めた．白色調領域はMUC5AC陽性細胞が主体であったが，構造異型・細胞異型は軽微で胃型（腺窩上皮型）腺腫と診断した．

　A 60-year-old male with suspected early gastric cancer during a previous hospital visit was presented to our hospital. The patient tested negative for Helicobacter pylori and had no history of eradication therapy. Endoscopic examination revealed a flat-elevated lesion at the fornix of the stomach. White light endoscopy revealed a lesion consisting of strongly-reddish, slightly-reddish, and whitish areas. The strongly-reddish area showed irregular microvessel patterns using magnified narrow-band imaging. Endoscopic findings suggested a well differentiated adenocarcinoma and endoscopic submucosal dissection was performed. The strongly-reddish area corresponded to low-grade well-differentiated adenocarcinoma with irregularly mixture of MUC6 and MUC5AC positive tumor cells. The slightly-reddish area was identified as typical gastric-type adenoma with MUC6 and MUC5AC expression. Meanwhile, the whitish area was diagnosed as gastric-type adenoma as well mainly consisting of foveolar-epithelial type tumor cells with MUC5AC expression.