いわゆる非腫瘍性RLHと胃MALTリンパ腫の鑑別診断―X線・内視鏡所見および超音波内視鏡所見による検討

Differential Diagnosis between So-Called Reactive Lymphoid Hyperplasia (RLH) and Mucosa-Associated Lymphoid Tissue (MALT) Lymphomas in the Stomach: Studies on Radiographic, Endoscopic, and Endosonographic Findings

要旨　1988年以降の非腫瘍性RLH，低悪性度および高悪性度MALTリンパ腫を対象とし，3群のX線・内視鏡・超音波内視鏡（EUS）像を検討した．X線・内視鏡上，凹凸顆粒状粘膜，多発びらん・潰瘍は3群に共通して認められたが，低悪性度MALTリンパ腫は易出血性，Ⅱc様陥凹の頻度が高く，他所見も合併し多彩な像を呈した．高悪性度MALTリンパ腫は上記に加えて粘膜下腫瘍様隆起，耳介様周堤を高率に認めた．EUS上，非腫瘍性RLHが単独所見（第2，3層の肥厚）のみが多いのに対し，低悪性度MALTリンパ腫は2，3の所見が複合したものが優勢で，高悪性度MALTリンパ腫では低エコー性腫瘤形成に他の2，3の所見が複合して認められた．所見の共通性から非腫瘍性RLHが低悪性度MALTリンパ腫の前段階である可能性が示唆され，MALTリンパ腫群のほうで，所見がより多彩，複合化する傾向を認めた．H. Pylori感染率は非腫瘍性RLHで100％，低悪性度MALTリンパ腫で70％，高悪性度MALTリンパ腫では50％であった．また，低悪性度MALTリンパ腫でも深達度sm深部以上になるとリンパ節浸潤は高率であった．以上の結果から，非腫瘍性RLHと低悪性度MALTリンパ腫の鑑別診断は，臨床上極めて重要であり，多彩なX線・内視鏡所見とEUS所見を組み合わせることによってある程度可能であることが示唆された．

　We investigated radiographic, endoscopic and endosonographic (EUS) findings in 28 patients with gastric mucosa-associated lymphoid tissue (MALT) lymphomas (low-grade 20, high-grade 8) and 9 patients with non-neoplastic lymphoid hyperplasia (so-called RLH), who were diagnosed in our institute between 1988 to 1995. The diagnosis of RLH was made histologically from large specimens including the submucosal layer, and utilizing EUS and EMR (endoscopic mucosal resection) technique. Diffuse granular mucosa and multiple erosions were the most common radiographic and endoscopic findings. Friable mucosa and depressed lesions (simulating early gastric cancer of Ⅱc type) were more frequently seen in cases of low-grade MALT lymphomas than in those of RLH. In cases of high-grade MALT lymphomas, submucosal ulcerating tumors combined with other various findings were characteristic. EUS showed simple findings (thickening of the second to third layers) in cases of RLH, while low-grade MALT lymphomas had multiple abnormal EUS findings. In cases of high-grade MALT lymphomas, hypoechoic mass mixed with other findings was seen on EUS. These findings suggested that RLH must be a precursor of low-grade MALT lymphoma, which showed more mixed and compound findings. The Helicobacter pylori infection rate was 100% in RLH, 70% in low-grade, and 50% in high-grade MALT lymphomas. Low-grade MALT lymphomas with deep submucosal infiltration were a high risk group for lymph node infiltration. In view of our results, the combination of radiographic, endoscopic, and EUS findings seemed to be useful to some extent in the differential diagnosis of RLH and low-grade MALT lymphomas of the stomach.