肺腫瘍疑いで経過観察中，失神を繰り返し突然死した肺動脈平滑筋肉腫の1例

A Patient with Pulmonary Intimal Sarcoma who Died Suddenly after Repetitive Syncope during Investigation of Suspected Lung Cancer

要旨　患者は53歳，女性．咳，息切れが生じ近医にて肺炎の治療を受けていたが，胸部CTより肺腫瘍が疑われ当院呼吸器科を紹介された．気管支鏡検査を施行するも診断がつかず経過観察されていたが，3回失神したため再入院した．理学的所見として収縮期雑音を聴取，肝を触知し，下腿浮腫を認めた．諸検査にて著明な右心系の拡大，圧負荷が疑われた．入院4日目早朝，トイレから部屋に戻る途中に突然倒れた．心肺停止状態でCPRの甲斐なく永眠された．剖検にて，肺動脈弁を一部巻き込んで肺動脈主幹部から左右肺動脈分枝部まで肺動脈内腔をほぼ完全に閉塞する腫瘍を認めた．組織学的には楕円形核を持つ紡錘形細胞が増殖し，平滑筋肉腫と診断された．肺動脈平滑筋肉腫は極めて稀な疾患であり予後不良とされるが，早期発見し外科的完全切除を行うことが予後を改善する唯一の方法と考えられるため，実地臨床家の本疾患の認知が重要である．

　A 53-year-old　female complaining of a cough and shortness of breath had been treated by a family doctor for pneumonia. She was referred to the respiratory department of our hospital for investigation of lung cancer suspected after plain chest computed tomography. However, a bronchoscopic examination revealed no malignant lesion. After leaving hospital, she experienced syncope three times and was referred to the cardiology department. She had musical systolic murmur, enlargement of the liver and edema in both legs. Right ventricular hypertrophy and pressure-overload were revealed by the electrocardiogram and echocardiogram. On the fourth day after admission, she died suddenly after returning from the restroom in the early morning. An autopsy demonstrated a large elastic mass which almost completely obstructed the main pulmonary artery from the pulmonary valve to the bifurcation of the pulmonary trunk. Histologically, the tumor was composed of spindle-shape tumor cells, which led to the diagnosis of leiomyosarcoma with the aid of immunohistochemical stain. Pulmonary intimal sarcoma is very rare and lethal, and can be difficult to identify due to the elusive nature of the disease. Therefore, an early diagnosis and surgical treatment may be necessary to improve a poor prognosis.