術前に確定診断に至らなかった隆起型胃MALTリンパ腫の1例

Protruded Type of Gastric MALT Lymphoma, Definitively Diagnosed Only After Endoscopic Submucosal Dissection Performed, Report of a Case

要旨●患者は60歳代，男性．近医にて6年間経過観察し，増大を認め，胃粘膜下腫瘍の精査のため当科に紹介となった．胃体下部前壁に径30mm大の立ち上がりがなだらかな粘膜下腫瘍を認め，表面は正常粘膜に覆われていた．超音波内視鏡検査では，第2〜3層に主座を置く低エコーの腫瘤を認め，内部に無エコーを伴う線状エコーを認めた．第一に異所性膵を疑い，全生検目的にてESDを施行した．病理組織学的検索では，表層は正常粘膜に被覆され，粘膜下層に小型〜中型の異型リンパ球がびまん性に増殖し，一部に結合組織を認めた．免疫組織化学的検索では，異型リンパ球はCD20，CD79aを発現しており，胃MALTリンパ腫と診断した．ESD施行後より3年経過し，現在再発なく経過中である．

　A 60-year-old man underwent EGD（esophagogastroduodenoscopy）6 years ago. A 10mm submucosal tumor was found in the gastric body. The lesion increased in size ; therefore, he was referred to our hospital. EGD revealed a broad-based protruded submucosal tumor, 30mm in size, covered with normal gastric mucosa. Endoscopic ultrasonography revealed the tumor to be a hypoechoic mass located mainly in the third layer of the gastric wall. A small anechoic area was also observed. We suspected heterotopic pancreas of the stomach, and ESD（endoscopic submucosal dissection）was performed for definitive diagnosis. Histologically, small and uniform lymphocytes were 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, and the clinical stage was identified as Stage I（Lugano International Classification）. He did not develop any recurrence 3 years after the ESD.