胃悪性リンパ腫および類似病変の画像診断―低悪性度リンパ腫（MALTリンパ腫）を中心に

Image Diagnosis of Gastric Malignant Lymphoma and its Mimicking Lesions: Focused on the Low-grade Malignant Lymphoma (MALT Lymphoma)

要旨　(1)病理組織学的に胃原発性悪性リンパ腫と診断された79例について肉眼型と組織型を比較した．腫瘤形成型の大部分は組織学的に高悪性度リンパ腫であり，表層拡大型の多くは低悪性度リンパ腫であった．(2)低悪性度リンパ腫であるMALT（mucosa-associated lymphoid tissue）リンパ腫の特徴ならびに臨床的位置づけを明確にするために表層拡大型悪性リンパ腫および悪性リンパ腫と鑑別が必要なリンパ腫類似病変，すなわち良・悪性境界領域病変3例，ALH（atypical lymphoid hyperplasia）7例，BLH（benign lymphoid hyperplasia）5例を対象に肉眼所見，X線所見ならびに内視鏡所見を検討した．(a)X線所見：多数ないし密在する大小顆粒状陰影と散在する小陰影斑は良・悪性境界領域病変，MALTリンパ腫，ALHに多く，不整網状陰影は良・悪性境界領域病変，MALTリンパ腫に多く認められた．しかし，組織学的な悪性度との間に有意な関係はみられなかった．(b)内視鏡所見：白色調粘膜の中の発赤斑や易出血所見は各病型に認められ，悪性度の判定指標にはならなかった．敷石状所見は良・悪性境界領域病変とALHに多く見られたが，MALTリンパ腫には40％と少なかった．以上のことから，今のところ各病型は表層拡大型の低悪性度リンパ腫として包括して位置づけるべきで，前述したX線所見や内視鏡所見は表層拡大型の低悪性度リンパ腫に共通した特有な所見の1つと解釈すべきであると思われた．

　Macroscopic type was compared with histologic type on 79 cases of pathohistologically proven primary gastric malignant lymphoma. Most of the mass forming type was histologically diagnosed as high-grade malignant lymphoma, whereas many of the superficial spread type and giant fold type were low-grade malignant lymphoma. To clarify characteristics and clinical position of MALT (mucosa-associated lymphoid tissue) lymphoma which is low-grade malignant lymphoma, the following lesions were evaluated by the macroscopic, radiologic and endoscopic findings; the superficially spread malignant lymphoma, and the lymphoid lesions which need to be differentiated from malignant lymphoma, such as three cases of the borderline between benign and malignant lesions, seven cases of ALH (atypical lymphoid hyperplasia), and five cases BLH (benign lymphoid hyperplasia). a) Radiologic findings; a large number of or densely aggregated various sized shadows, and scattered small speckled shadows were seen in the borderline between benign and malignant lesions, MALT lymphoma and ALH lesions Irregular reticular shadows were found in the borderline between benign and malignant lesions and MALT lymphoma. But there was no significant correlation between shape and histological degree of malignancy. b) Endoscopic findings; red spots and bleeding tendency on the whitish mucosa were seen in each type of the lesions but did not indicate degree of malignancy. Cobblestone appearance was commonly found in the borderline between benign and malignant lesions and ALH, but it was seen in only 40% of MALT lymphoma. In conclusion, each type should be recognized comprehensively as the superficially spread type low-grade malignant lymphoma, and previously mentioned radiologic and endoscopic findings may be specific and common to the superficially spread type low-grade malignant lymphoma.