MALTリンパ腫との鑑別が困難であった十二指腸follicular lymphomaの1例

Follicular Lymphoma Mimicking Mucosa-Associated Lymphoid Tissue (MALT) Lymphoma of the Duodenum, which Improved after Helicobacter pylori Eradication, Report of a Case

要旨　症例は59歳，女性．健診異常の精査としての上部消化管内視鏡検査で十二指腸下行脚の顆粒状病変を認め，MALTリンパ腫を疑ったが，生検では確定診断に至らなかった．1年1か月後の生検でlow grade MALTリンパ腫の診断を得たが，内視鏡所見上は改善傾向を認めた．尿素呼気試験，病理組織と培養ではHelicobacter pylori（以下 Hp)陰性，血清Hp抗体のみ陽性であった．除菌療法を施行し，再発なく経過している．その後の病理，免疫組織学的検討にて，CD20，CD10，bcl-2陽性であり，初回検査時よりfollicular lymphomaであったとの診断に至った．MALTリンパ腫との組織学的な鑑別が困難であり，Hp除菌療法が有効であった1例として，ここに報告する．

　Malignant lymphoma of the duodenum is a rare disease. MALToma in the stomach has been intensively investigated, but in the duodenum it is so rare that its characteristic appearance has not been described in detail.

　Besides, differential diagnosis between MALToma and other malignant lymphoma, (follicular lymphoma, mantle cell lymphoma) is difficult.

　A 59-year-old woman who had taken a medical examination was transferred to our hospital for the further examination. The first endoscopic examination showed multiple tiny round nodules in the duodenum. Biopsy specimen revealed lymphoid follicles, and immunohistochemical examination revealed negative immunoreactivity for CD10 but positive immunoreactivity for CD20. We were not able to diagnose the lesion as MALToma. Concerning H. pylori, only serum Hp antibody was positive. After thirteen months, endoscopic examination showed that the round nodules had spontaneously reduced.

　However, at this time, immunohistochemical findings revealed immunoreactivity positive for CD20 and negative for CD10 and bcl-2, so we diagnosed the lesion as MALToma. We performed eradication therapy. Seventeen months after eradication of Hp, the tiny round nodules were found to have reduced.

　Afterwards, we investigated the immunohistology of the lymph folliclar lesion positive for CD10 and bcl-2, which was seen at the first examination.

　This enabled us to diagnose this case as follicular lymphoma from the beginning.

　In future, we should investigate many such cases so as to make accurate diagnosis and provide effective treatment for this type of lymphoma.