H. pylori未感染胃の前庭部に発生した胃型分化型早期胃癌の2例

H. pylori-negative Intramucosal Well-differentiated Tubular Adenocarcinoma of the Gastric Antrum with a Gastric Phenotype, Report of Two Cases

要旨●H. pylori未感染胃の前庭部に発生した胃型分化型早期胃癌の2例を報告する．［症例1］40歳代，男性．前庭部前壁の単発，3mm大の隆起性病変．［症例2］60歳代，女性．隆起型びらんが散在する前庭部前壁の周囲より目立つ5mm大の隆起性病変．EGDで両症例ともに萎縮なし，尿素呼気試験陰性，H. pylori血清抗体陰性であった．生検でtub1の診断でESDを施行した．病理組織学的所見はともに粘膜内のtub1で周囲は非萎縮幽門腺粘膜であった．免疫組織化学染色でMUC5AC，MUC6陽性，MUC2，CD10，pepsinogen I，H^＋/K^＋-ATPase陰性で胃型形質を示した．H. pylori未感染胃癌は前庭部では印環細胞癌が多いと報告されているが，分化型癌が発生する場合もあり，単発の粘膜変化や多発びらんの中でも目立つものに関しては注意が必要である．

　We report two cases of differentiated early gastric cancer with gastric mucous phenotype in the antrum of H. pylori（Helicobacter pylori）-negative stomach. Case 1 was a man in his 40s presenting with a single elevated 3mm lesion on the anterior wall of the antrum. Case 2 was a woman in her 60s presenting with an elevated 5mm lesion on the anterior wall of the antrum, surrounded by multiple elevated erosions. In both cases, endoscopic examination showed no atrophy, negative urea breath test, and negative serum antibody to H. pylori. Because the biopsy samples taken from these lesions showed well-differentiated tubular adenocarcinoma（tub1）, endoscopic submucosal dissection was performed. A histopathological diagnosis of tub1 confined to the mucosa was made. Mucosa outside the lesion composed of pyloric gland mucosa with no evidence of atrophic change or intestinal metaplasia. Tumor cells were positive for MUC5AC and MUC6, and negative for MUC2, CD10, pepsinogen I, and H^＋/K^＋ ATPase. Previous studies show that signet-ring cell carcinoma is most common in the antrum of H. pylori-negative stomach. However, differentiated gastric cancer can also occur. Careful examination is required to observe potential single mucosal changes and prominent erosions surrounded by multiple erosions even in a regular arrangement of collecting venules-positive stomach.