Primary peri-aortic hemangiosarcoma in a dog.

A 10-year-old intact male Norwich terrier dog was evaluated for progressive, intermittent increased respiratory effort. Thoracic radiographs, ultrasonography, and computed tomography were used to identify a caudodorsal thoracic extrapulmonary mass and the presence of pulmonary metastasis. Blood transfusion and stabilization measures were not successful and the patient died. Necropsy confirmed the origin of the mass to be the adventitial layer of the aorta and determined it to be hemangiosarcoma. This is a rare site for the primary lesion.