[Intrathoracic chronic expanding hematoma; report of a case]

A case of a patient with a intrathoracic chronic expanding hematoma presenting as a neoplasm is reported. A chronic encapsulated intrathoracic hematoma is rare condition and is clinically included in a category of chronic hemorrhagic empyemas as a type of chronic empyemas in Japan. The clinical picture of our case suggested a slowly growing tumor. Though needle biopsy was performed, only blood was aspirated. Intraoperative findings revealed a intrathoracic hematoma with a tough capsule. It adhered to the chest wall hardly. Histopathological investigations revealed that the capsule consisted of a collagenous outer layer and a newly vascularized inner layer with fibrosis. Hemosiderin deposits suggested recurrent bleeding from fragile vessels. The mechanisms of hematoma formation and its expanding nature are discussed. The hematoma appeared to have been enlarged by repeated exudation or bleeding from capillaries inside the capsule.