1年間で著明な形態変化を認め，最終的に進行癌であった胃型低異型度分化型胃癌の1例

Marked Morphological Change in a Gastric-type, Low-grade, Well-differentiated Adenocarcinoma of the Stomach in 1 Year, Report of a Case

要旨●患者は70歳代，男性．10年前に早期胃癌に対してESDを受け，以後1年ごとにEGDで経過観察をされていた．1年前のEGDで胃穹窿部大彎に10mm程度の扁平隆起性病変を認めたが，生検病理組織学的診断でGroup 2と診断されたため経過観察となった．今回同病変は20mm大の半球状の隆起性病変に増大し，NBI拡大観察では境界明瞭で大小不同を有する不整なvilli様構造を呈していた．生検病理組織学的診断ではGroup 4と診断され，ESDを行った．病理組織像では表層は腺窩上皮型の異型の乏しい腺癌で，粘膜下に浸潤していた．細胞形質はMUC5AC，MUC6陽性で，胃型低異型度分化型胃癌と診断した．深部断端陽性で脈管侵襲を認めたため追加手術を行った．

　A 70-year-old man underwent endoscopic submucosal dissection for early gastric cancer 10 years ago, following which he received esophagogastroduodenoscopy every year. During follow-up, a flat elevated lesion measuring 10mm in size was detected in the greater curvature at the fornix of the stomach. Biopsy specimens were diagnosed as group 2. After 1 year, the lesion progressed to a hemispherical elevated lesion measuring 20mm in size. Narrow-band imaging with magnification revealed an irregular mucosal surface pattern of villi-like structure. Based on the biopsy specimens, an extremely well-differentiated adenocarcinoma was suspected. We performed endoscopic submucosal dissection. A pathological examination revealed that the superficial layer of the lesion was very mild atypia of foveolar-type adenocarcinoma, and the tumor invaded to the submucosal layer. Furthermore, the tumor cells were positive for MUC5AC and MUC6 ; therefore, we diagnosed the lesion as a gastric-type, low-grade, well-differentiated adenocarcinoma of the stomach. The vertical margin of the resected specimens was positive with the involvement of vessels, and the patient was subsequently subjected to total gastrectomy.