胃MALTリンパ腫（low-grade malignant B-cell lymphoma of mucosa-associated lymphoid tissue）32例の臨床像

Clinical and Pathological Features in 32 Cases with Low-grade Gastric Lymphoma of Mucosa-associated Lymphoid Tissue

要旨　1965年から1993年3月までの間に手術され，病理学的検索にて胃のlow-grade B-cell lymphoma of mucosa-associated lymphoid tissue（胃MALTリンパ腫）と診断された32例（1983年のIsaacsonらの基準に従って見直し診断した症例を含む）を対象とし，臨床および病理学的検討を行った．1965年から1987年までの間に診断された20例の初回診断は，17例がreactive lymphoreticular hyperplasia（RLH），2例がRLH＋悪性リンパ腫（ML），1例がMLと診断されていた．一方，1988年以降に診断された12例はすべてMLと初回診断されていた．粘膜下層までに限局した早期MALTリンパ腫の組織診断は，通常生検標本のみでは困難な場合も多く，最近の症例では5例に対しstrip biopsyを行い，確定診断を得た．MALTリンパ腫を早期群（22例）と進行期群（10例）に分けて，その臨床像を比較検討したところ，前者に女性例が多く，後者に病悩期間が長いものが多かった，両群ともX線・内視鏡上いわゆる表層拡大型の形態を呈し，びまん性凹凸顆粒状粘膜，多発びらんおよび小潰瘍，Ⅱc様不整陥凹などが高頻度に認められたが，進行期群でX線上の伸展不良が顕著であった．超音波内視鏡所見では，早期群と進行群期で明らかな差異を認め，両群の鑑別に有用であった．病理組織学的検索の結果，MALTリンパ腫にhigh-grade componentを合併した症例が2例存在した．また，進行期群の3例ではリンパ節転移が認められた．長期経過観察例の検討では進行が遅く長期間胃に限局するが，末期には全層浸潤，リンパ節転移を来すことが示唆された．MALTリンパ腫は臨床的にもlow-grade malignancyとして対応し，できるだけ早期に診断・治療することが予後の向上につながると考えられる．

　To determine the clinical and pathological features of low-grade gastric lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma), 32 surgical cases were studied. Of 20 cases which were operated on during the period from 1965 to 1987, 17 had been initially diagnosed as reactive lymphoreticular hyperplasia (RLH), and 2 as malignant lymphoma (ML) combined with RLH. Twelve cases which were operated on during the period from 1988 to 1993 had been initially diagnosed as malignant lymphoma. In 5 cases with early MALT lymphomas, conventional endoscopic forceps biopsy did not provided a definite histologic diagnosis, so endoscopic mucosal resection was performed to obtain specimens large enough to include the submucosa.

　All 32 cases were divided according to the depth of the tumor into two groups: early stage group (22 cases) and advanced stage group (12 cases). Clinical and pathological features in these two groups were compared. As a result, there was a female predominance in the early stage group, and the duration of the disease was relatively longer in the advanced stage group. Radiography and endoscopy frequently demonstrated various findings such as diffuse granular mucosa, multiple erosions and ulcers, and depressed lesion simulating Ⅱc-type early gastric cancer in both groups. Endoscopic ultrasonography revealed two characteristic patterns: “superficially spreading type” in the early stage group, and “diffusely infiltrating type” in the advanced stage group. In 2 cases, histologic evaluation showed high-grade lymphoma combined with MALT lymphoma. Para-gastric lymph node involvement was evident in 3 patients of the advanced stage group.

　It is suggested that MALT lymphoma shows slow infiltrative growth and remains confined to the stomach for long periods of time. In some cases, however, transmural infiltration and spread beyond para-gastric lymph nodes may occur during the long-term follow-up period. Therefore, MALT lymphoma should be clinically treated as low-grade malignancy. The early diagnosis of this disease is essential for better prognosis.