胃MALTリンパ腫の生検診断

Histologic Diagnosis of Primary Gastric Lymphoma of Mucosa-Associated Lymphoid Tissue Type through Endoscopic Biopsy Specimen

要旨　胃原発MALTリンパ腫の診断は，臨床医のみならず病理医にとっても難しい．今回，外科的切除が行われたMALTリンパ腫15例を低悪性度10例，高悪性度5例に分類し，生検材料を病理学的に検討した．低悪性度MALTリンパ腫の生検診断に重要な組織学的所見は，細胞浸潤の程度，lymphoepithelial lesion，細胞異型の有無であった．診断上鑑別を要する病変として，良性炎症性病変，印環細胞癌，低分化腺癌，形質細胞腫，他の悪性リンパ腫が考えられた．更に，良性炎症性病変との鑑別にサザンプロット法による遺伝子解析が有用と思われた．高悪性度MALTリンパ腫の生検診断は容易であったが，肉眼形態からも低悪性度病巣内に高悪性度病変が存在することが推察可能であった．

　A definitive diagnosis of primary gastric lymphoma of mucosa-associated lymphoid tissue (MALT) may be often difficult not only for clinicians but also for pathologists. In this study, we reevaluated histologic criteria for the diagnosis through endoscopic biopsy specimens of 15 cases of surgically resected MALT lymphomas, which were classified into low-grade (n=10) and high-grade (n=5). Recognition of dense lymphoid infiltrate, prominent lymphoepithelial lesion, and moderate cytologic atypia was important for the diagnosis of low-grade MALT lymphoma. Benign inflammatory infil-trate, signet-ring cell carcinoma, poorly differentiated adenocarcinoma, plasmacytoma, and the other types of low-grade lymphoma were considered as differential diagnoses. The detection of immunoglobulin heavy-chain gene rearrangement by Southern blot hybridization from biopsy specimens was useful to distinguish low-grade MALT lymphoma from benign inflammatory infiltrate. To make a histologic diagnosis of high-grade MALT lymphoma was not so difficult and the characteristic features of its gross appearance also suggested the possible presence of high-grade MALT lymphoma with low-grade component.