Hemothorax in Three Dogs with Intrathoracic Extracardiac Hemangiosarcoma.

Intrathoracic extracardiac hemangiosarcoma (HSA) is rare in dogs. This report describes three dogs with acute onset dyspnea due to hemorrhagic pleural effusion resulting from intrathoracic extracardiac masses, which were confirmed as HSA by histopathology. The dogs were stabilized with thoracocentesis and intravascular fluid resuscitation. Computed tomography identified intrathoracic masses, which were not originating from the heart or pulmonary parenchyma. Surgical exploration was performed in all cases. Case 1 was euthanized intraoperatively as the tumor could not be dissected from the aorta. In cases 2 and 3, hemostasis and resection of the tumors was successful. Case 2 was euthanized 1 mo after surgery and case 3 was alive at the time of writing, 5 mo postoperatively. Intrathoracic extracardiac HSA should be considered as a differential for nontraumatic hemothorax and surgical treatment can be palliative.