非乳頭部十二指腸上皮性腫瘍との鑑別診断に拡大観察が有用であった十二指腸異所性胃粘膜の1例

Duodenal Ectopic Gastric Mucosa Where a Magnified Observation was Useful for the Differential Diagnosis of Non-ampullary Duodenal Epithelial Tumor, Report of a Case

要旨●十二指腸3rd portionに，ほぼ境界明瞭な発赤陥凹を認め，内部に白濁した絨毛様構造が散在していた．NBI拡大観察にて，大小不同なvilli様構造が低密度に存在し，背景粘膜との境界は不明瞭であった．一部のvilliは辺縁が白濁し，white zoneが不均一に肥厚していたが，陥凹部では整形なpit様構造を認めた．腫瘍と非腫瘍を示唆する所見が混在していたが，villi様構造の大小不同とwhite zoneの不均一な肥厚を優位と判断し，小腸型の高分化管状腺癌と診断した．underwater EMRにて一括切除したところ，病理組織学的には異所性胃粘膜であった．white zoneが不均一に肥厚したvilli部の深部にはCDX-2陽性，MUC2陽性の腺管があり，表層部では一部CD10陽性で，異所性胃粘膜内に発生した小腸上皮化生と診断した．retrospectiveに検討すると，陥凹部に整形のpit様構造が認められたことから，異所性胃粘膜と診断することは可能であったと考えられた．十二指腸の陥凹型異所性胃粘膜は極めてまれな病変だが，十二指腸に発赤陥凹を認めた場合は，本疾患を念頭に置いて，鑑別診断を行うべきと思われた．

　A well-demarcated, erythematous depressed lesion was observed in the 3rd portion of the duodenum, and partially cloudy villous-like structures was shown inside the lesion. Narrow-band imaging magnified endoscopy revealed low-density villous-like structures of various sizes, with an unclear demarcation between the lesion and the background mucosa. Edge of some villi was whitish, and the white zone was unevenly thickened, however regular pit-like structures were observed in the depressed area. Although the findings suggested a mixture of neoplastic and non-neoplastic lesions, it was diagnosed as a well-differentiated adenocarcinoma based on villous-like structures of various sizes and uneven thickening of the white zone. En bloc resection by underwater endoscopic mucosal resection was performed, and the final histological diagnosis was ectopic gastric mucosa. CDX-2- and MUC2-positive glands were noted in the deep part of the villi, where the white zone is unevenly thickened, and CD10 was positive in some superficial areas. Hence, it was diagnosed as intestinal metaplasia in the ectopic gastric mucosa. Retrospectively, a diagnosis of ectopic gastric mucosa was possible because a regular pit-like structure was observed in the depressed part. Although a depressed ectopic gastric mucosa of the duodenum is extremely rare, when an erythematous depression is observed in the duodenum, a differential diagnosis between neoplastic and ectopic gastric mucosa should be considered.