粘膜下腫瘍様形態を示したHelicobacter pylori陰性胃MALTリンパ腫の1例

MALT Lymphoma without Helicobacter pylori Infection Taking the Form of Submucosal Tumor, Report of a Case

要旨　患者は50歳代，男性．心窩部痛，黒色便を主訴に近医を受診した．胃内視鏡検査および胃X線検査で，噴門直下小彎に，潰瘍形成を頂部に伴う粘膜下腫瘍様隆起性病変を認めた．出血を伴う胃悪性腫瘍と術前診断し，噴門側胃切除を行った．病理組織学的には粘膜の深層から固有筋層にかけてリンパ濾胞を伴い，その周囲に小型の異型リンパ球のびまん性増生を認め，HP（Helicobacter pylori）陰性の胃MALTリンパ腫と診断された．HP陰性胃MALTリンパ腫は除菌療法効果が少ないとされる．また，その肉眼形態に関して見解の統一はなされていないが，粘膜下腫瘍様形態をとる病変では，本症を鑑別の上位に挙げることが治療のうえで重要と考えられた．

　A fifty-year-old male presented with melena and upper abdominal pain. X-ray and endoscopic examination showed a protruding lesion that appeared to be a submucosal tumor with an ulcer at the lesser curvature in the cardia of the stomach. We clinically diagnosed gastric malignant tumor without Hp（Helicobacter pylori）infection and performed cardiac resection of the stomach. Histologically, small and uniform lymphocytes had diffusely proliferated with lymphoid follicles between the mucosal layer and the muscularis propria of the gastric wall. We finally diagnosed a gastric marginal zone lymphoma of mucosa-associated lymphoid tissue（MALT lymphoma）. The macroscopic characteristics of gastric MALT lymphoma without Hp infection are not well known, but such lesions are known to be unresponsive to Hp eradication. It is important for the treatment of gastric tumor that MALT lymphoma be ruled out when making a differential diagnosis of gastric submucosal tumor without Hp infection.