胃MALTリンパ腫と反応性リンパ腫の鑑別診断に関する検討―内視鏡的粘膜切除法と遺伝子診断の有用性

Differential Diagnosis between MALT Lymphoma and Reactive Lymphoreticular Hyperplasia of the Stomach

要旨　胃MALTリンパ腫22例と反応性リンパ腫（RLH）12例を対象にして両疾患の鑑別方法を中心に検討した．内視鏡所見および鉗子生検所見では両者を明確に区別することが困難な症例が認められた．一方，診断目的で施行した内視鏡的粘膜切除法（EMR）により，MALTリンパ腫の6例中5例（83.3％），RLHの4例中4例（100％）で確定診断が可能で，EMRによるjumbo biopsyは有力な診断方法と考えられた．また，MALTリンパ腫に対する遺伝子診断の感度は60.0％，特異度100％，正診率76.0％で，感度はやや低いものの特異度に優れ，補助診断法として有用と思われた．Helicobacter pylori（以下H. pylori）の陽性率はMALTリンパ腫で95.2％，RLHでは100％と高率で，除菌治療によって著明に改善した症例を認めたことから，H. Pyloriは両疾患と深い因果関係があることが示唆された．様々な方法を用いても鑑別が困難な場合は，H. Pyloriの存在を確認してまず除菌療法を行い，治療効果をみることが第1選択の治療法と考えられる．

　Twenty-two cases of MALT lymphoma and 12 cases of reactive lymphoreticular hyperplasia (RLH) were evaluated retrospectively. Endoscopic findings and histological findings of conventional biopsy could not definitively distinguish MALT lymphoma from RLH in all cases. Jumbo biopsy using endoscopic mucosal resection (EMR) was performed in 10 cases (MALT lymhoma six cases, RLH four cases), and definitive diagnosis was able to be obtained in 5 of 6 cases (83.3%) and in 4 of 4 cases (100%) respectively. Diagnostic EMR was thought to be a useful procedure for the diagnosis of MALT lymphoma and RLH. Molecular biological techniques using polymerise chain reaction (IgH-PCR) revealed monoclonal band in 9 of 15 cases (60.0%) with MALT lymphoma, but in none of the 10 cases with RLH. Sensitivity was not so good (60.0%) but specificity was high (100%). For these reason, IgH-PCR should be regarded as one of the supplementary procedures for the diagnosis. Highly positive rate of Helicobacter pylori (H. pylori) was recognized in the cases of MALT lymphoma (95.2%) and RLH (100%). Eradication therapy was successful in two cases of MALT lymphoma and in 10 cases of RLH, and it was suspected that H. pylori played a significant role in both diseases. If definite diagnosis is still difficult despite the above examinations, eradication therapy for H. pylori should be performed as the first choice of treatment.