急性骨髄性白血病治療後に診断されたIMT（inflammatory myofibroblastic tumor）の1例

Inflammatory Myofibroblastic Tumor which Developed after Chemotherapy and Auto-peripheral Blood Stem Cell Transplantation for Acute Myeloid Leukemia, Report of a Case

要旨　患者は64歳，男性．急性骨髄性白血病治療後に貧血を認めたため，その原因精査のために大腸内視鏡検査を施行したところ，回盲弁上に基部を有する30mm大の亜有茎性隆起性病変を認めた．病変の表面は凹凸不整で結節顆粒状を呈し周囲の背景粘膜には炎症性変化を認めた．腫瘍性病変を疑い病変部から数か所生検を行ったが確定診断には至らなかった．本例は1年10か月前に便潜血陽性のため施行した大腸内視鏡検査で同部に明らかな異常を認めておらず，病変はその後に出現，増大したことが示唆された．病変の増大傾向を考慮して，回盲部切除術を施行した．切除標本を病理組織学的に検討すると，病変はリンパ球と形質細胞の浸潤を伴う大小不同の紡錘形細胞の束状増殖から成り，α-SMA陽性，vimentin陽性などの免疫染色の結果と併せて炎症性筋線維芽細胞性腫瘍（inflammatory myofibroblastic tumor ; IMT）と確診された．本例はその臨床経過から比較的急速な増大傾向が示唆され，IMTの発育進展を考えるうえで貴重な症例と考えた．

　A 64-year-old male was admitted to our institution with the complaint of anemia and positive fecal occult blood. He had undergone chemotherapy and auto-peripheral blood stem cell transplantation for acute myeloid leukemia from March to October, 2006. Barium enema study revealed a semipedunculated polypoid lesion, measuring 30mm in size, on the ileo-cecal valve. Colonoscopy disclosed a lesion mass, reddish in color, whose surface was irregular and nodular. Ulcer scars were also seen in the surrounding mucosa. Because endoscopy had not revealed any abnormality one year and ten months previously, and the lesion seemed to have enlarged rapidly, ileo-cecal resection was performed. Histological examination of the resected specimen showed proliferation of spindle-shaped cells with infiltration of lymphocytes and plasma cells. Inclusing immunohistochemical study, the mass was diagnosed as an inflammatory myofibroblastic tumor（IMT）. Further clinical studies are warranted to clarify the nature of IMT.