胃底腺粘膜に発生する腫瘍の組織分類の新展開—胃底腺粘膜に発生する腫瘍の内視鏡診断

Endoscopic Diagnosis of Gastric Epithelial Neoplasia Arising from the Fundic Gland Mucosa

要旨●胃底腺粘膜に発生する胃腫瘍の中で，H. pylori未感染胃に発生する胃腫瘍の臨床病理学的・内視鏡学的特徴について概説した．今回，H. pylori未感染胃底腺粘膜に発生する胃腫瘍の中で，特に胃底腺型腺癌，胃底腺粘膜型腺癌，胃型分化型腺癌，胃型腺腫を抽出し解析した．細胞分化では，胃底腺型腺癌は胃底腺のみ，胃底腺粘膜型腺癌は腺窩上皮＋胃底腺（＋幽門腺），胃型分化型腺癌・胃型腺腫は腺窩上皮＋幽門腺（＋胃底腺）への分化を示し，通常型の胃癌に比較して異型度や悪性度は低く，内視鏡治療を選択された症例が多かった．内視鏡診断は，各タイプの特徴を理解したうえで，NBI併用拡大内視鏡診断と内視鏡所見から表層の腫瘍成分の有無，表層と上皮下の成分の関係性を推測することが，H. pylori未感染胃底腺粘膜に発生する胃腫瘍の内視鏡診断と各鑑別につながると考えられた．

　We analyzed the clinicopathological and endoscopic features of gastric epithelial neoplasia arising from the fundic gland mucosa in patients uninfected by Helicobacter pylori. Gastric epithelial neoplasia arising from the fundic gland mucosa was histopathologically classified into GAFG（gastric adenocarcinoma of fundic gland type）, GAFGM（gastric adenocarcinoma of fundic gland mucosa type）, GAGP（gastric adenocarcinoma of gastric phenotype）, and PGA（pyloric gland adenoma）. According to the cell differentiation findings, GAFG indicates differentiation toward fundic gland cells, GAFGM indicates differentiation toward foveolar cells and fundic gland cells, and GAGP and PGA indicate differentiation toward foveolar cells, pyloric gland cells and fundic gland cells. These neoplasms demonstrated a lower degree of atypia and malignancy than the common type of gastric cancer, and endoscopic resection was selected for treatment. The recognition of every endoscopic feature and the identification of tumor exposure on the surface and the relationship between surface mucosa and the underlying tumor are necessary for accurate endoscopic diagnosis of gastric epithelial neoplasia arising from the fundic gland mucosa in patients without H. pylori infection.