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症例は78歳の男性で,2004年9月腹部CTにて後腹膜嚢胞性腫瘤を指摘された.その後,腫瘤増大傾向を認めたため,手術目的に入院した.血液検査では腫瘍マーカーはいずれも基準範囲内であった.腹部CTおよびMRIでは,十二指腸水平部を下方より,腎下部下大静脈を右前方より圧排する長径6cmの嚢胞性腫瘤を認めた.2006年6月,経腹的に嚢胞摘出術を施行した.摘出標本の重量は94g,最大径6.4cmで,嚢胞壁は薄く,内容液は淡黄色,漿液性であった.病理組織学的検査所見では嚢胞壁,内容液に悪性所見はなかった.Masson trichrome染色Elastica-van Gieson染色で,脈管由来と診断し,CD31,CD34,FactorVIII,D2-40染色検査にて静脈由来の真性血液嚢胞(限局性静脈拡張症)と診断した.術後12病日に軽快退院し,再発は認めない.静脈由来の後腹膜嚢胞はまれであり,報告する.
A case of retroperitoneal venous aneurysm, which was found during screening examinations for swelling of the legs, is reported. A 78-year-old man was detected to have a cystic tumor in the retroperitoneum by computed tomography in September 2004. This tumor had increased in size during follow-up over twenty one months, therefore, the patient was admitted for operation. Computed tomography and magnetic resonance imaging revealed a cystic mass, 6cm in diameter, pressing the duodenum upward and inferior vena cava to the left and backward. Transperitoneal extirpation of the cystic tumor was conducted on June 26, 2006. The extirpated specimen was almost spherical and was encapsulated by a thin elastic wall, measured 6.4cm in maximum diameter and weighed 94g, and contained yellowish serous fluid. Microscopically, the cyst wall and contents showed no evidence of malignancy. The results of Masson's trichrome staining and Elastica von Gieson stainingsuggested that the tumor originated from a blood vessel. Immunohistochemically, the inner cells of the tumor were positive for CD31 and factor VIII, partially positive for CD34, and negative for D2-40. Based on these findings, the tumor was diagnosed to be a retroperitoneal venous aneurysm, which is a very rare condition. The patient remains well without recurrence at present, 14 months after the operation.