十二指腸球部に発生したWOS陰性の胃腸混合型腺腫の1例

WOS-Negative Adenoma of Gastrointestinal Phenotype Arising from Bulbus of the Duodenum, Report of a Case

要旨●60歳代，男性．EGDにて，十二指腸球部に約20mmの同色調〜発赤調で乳頭状構造を伴う丈の高い隆起性病変を認めた．NBI併用拡大観察では，さまざまな程度の窩間部の開大を認めるが，表面構造に不整は認めず，WOSは陰性であった．内視鏡的に胃型形質の十二指腸腺腫と診断しEMRを施行した．病理組織学的所見では，腺窩上皮と頸部粘液腺に類似する腫瘍が増生し，MUC5ACとMUC6に加えMUC2が陽性であり，胃腸混合型形質の十二指腸腺腫と診断された．十二指腸非乳頭部腫瘍は粘液形質別に特徴的な内視鏡所見を示すことが知られているが，時に病理組織学的所見と乖離する非典型例が存在することに留意する必要がある．

　This report describes the case of a male patient in his 60s who underwent EGD（esophagogastroduodenoscopy）for surveillance. EGD revealed a 20-mm reddish pedunculated lesion with a papillary structure in the first portion of the duodenum. Magnifying endoscopy with narrow-band imaging revealed a regular microsurface pattern with dilatation in various degrees of the intervening part, but a white opaque substance was not observed. This lesion was endoscopically diagnosed as duodenal adenoma with gastric phenotype, and endoscopic mucosal resection was performed. Histopathological examination showed duodenal adenoma resembling a foveolar epithelium and a mucous neck cell. Immunohistochemistry for phenotypes was positive for MUC5AC, MUC6, and MUC2 and negative for CD10, which is compatible with the gastrointestinal mucin phenotype. Although endoscopic findings on non-papillary duodenal tumors tend to show features characteristic to mucin phenotypes, some cases notably show a divergence between endoscopic and pathological findings.