[Case of rapidly progressing primary pulmonary rhabdomyosarcoma with bloody pleural effusion].

A 64-year-old man, complaining of dyspnea from the beginning of May 2006, was admitted to a local hospital because of bloody pleural effusion. After a drainage procedure of the right thoracic cavity was performed, he was referred to our hospital on May 15. Approximately one liter of bloody pleural effusion was drained every day. Computed tomography (CT) on admission showed right pleural effusion, a collapsed right lung and a large marginally enhanced low-density mass in the right lung field. We could not make a specific diagnosis even with a cytological examination of the pleural effusion and thoracoscopic pleural biopsy. Accordingly, open thoracotomy was performed and rhabdomyosarcoma was finally diagnosed. The tumor grew rapidly in a short period, and the patient died only one month after the onset of his complaint. Autopsy revealed primary pulmonary rhabdomyosarcoma occupying most of the right thoracic cavity, but no metastasis. Initially we could not identify the tumor by CT scan, mainly because it had the same density as muscle, nearly the same density as the pleural effusion and lower density than other lung cancers. Primary pulmonary rhabdomyosarcoma is rare. As this tumor could show unexpectedly fast growth, rapid diagnosis is essential. Therefore, we should include thoracic sarcoma in the list of differential diagnosis of rapidly growing lung tumors and bloody pleural effusion.