形質細胞への高度な分化を示した胃MALT型リンパ腫の1例

Low-grade B-cell Gastric Lymphoma of Mucosaassociated Lymphoid Tissue Exhibiting Marked Plasma Cell Differentiation, Report of a Case

要旨　患者は49歳，女性．嘔気，背部痛を主訴に来院した．胃X線検査，胃内視鏡検査で胃体上部前壁・大彎・後壁および胃体下部前壁に粘膜ひだの途絶した陥凹病変が存在した．陥凹部とその周囲は褪色調であった．同部の生検で胃形質細胞腫と診断され，胃全摘術を施行した．組織学的には胃上部前壁の陥凹部粘膜内に形質細胞が多数増殖しているが，lymphoepithelial lesionやcentrocyte-like cellの増殖もみられた．胃上部大彎後壁および胃中部前壁の陥凹部は，形質細胞の増殖がないほかは同様の所見であり，形質細胞への高度な分化を示した胃MALT型リンパ腫と診断された．本例は胃形質細胞腫との鑑別に難渋した症例で，MALT型リンパ腫の概念が導入された現在では，胃形質細胞腫症例の再検討が必要になると考えられた．

　A case of low-grade B-cell gastric lymphoma of mucosa-associated lymphoid tissue (MALT) exhibiting marked plasma cell differentiation is reported. A 49-year-old female patient was referred to the Fukui Prefectural Hospital complaining of nausea and back pain. X-ray and endoscopic examination revealed depressed lesions with interrupted mucosal folds and discoloration in the middle body of the stomach. Pathological examination of the biopsy specimen revealed plasmacytoma. The patient received total gastrectomy. Histologically, intense infiltration of centrocyte-like (CCL) cells was noticed spread in the mucosa and submucosa. These CCL cells formed lymphoepithelial lesions in the mucosa. Particularly, at the anterior wall of the upper body of the stomach, CCL cells demonstrated extreme differentiation from plasmacytes with monoclonal cytoplasmic immunoglobulin. Pathological diagnosis was low-grade B-cell gastric lymphoma of MALT. Because of the marked plasma cell differentiation, it was difficult to distinguish lymphoma of MALT from plasmacytoma of the stomach.