Excision of a locally invasive thymoma causing cranial vena caval syndrome in a dog

A 9-year-old female Golden Retriever was examined because of inappetance, labored breathing, edema, and distension of the veins of the neck. Thoracic radiography revealed pleural effusion and a cranial mediastinal mass. Biopsy results obtained by use of fine-needle aspiration were consistent with thymoma. At surgery, the tumor was found to have invaded the cranial vena cava. Extra- and intravascular portions were removed without complications, and the dog's clinical signs resolved. To our knowledge, this is the first documented report of an invasive thymoma causing cranial vena caval syndrome that has been successfully treated in a dog. In this instance, the simplest surgical method, namely venotomy and tumor extraction using venous inflow occlusion, was successful, obviating the need for temporary or permanent vascular conduits or grafts. These findings indicate that there is potential for surgical correction of invasive thymoma with cranial vena caval syndrome in some animals, and the prognosis is not always poor.