Thorax
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Publication Date: 2008-10-10
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History
11 year old male neutered Rhodesian Ridgeback. History of two episodes of choking on saliva and bringing up white foam.
Findings
There is a rounded soft tissue mass within the cranial mediastinum just cranial to the heart. There is diffuse gas distention of the esophagus. There are alveolar infiltrates within the right middle lung lobe. There is a rounded soft tissue mass at the left ventral thoracic wall which is external to the thorax. The cardiovascular structures are within normal limits.
DDx
The diagnosis that ties a cranial mediastinal mass together with megaesophagus and aspiration pneumonia is a thymoma with secondary myasthenia gravis. Other causes of cranial mediastinal masses include lymph node, cyst and granuloma. Megaesophagus can be idiopathic or acquired.
Diagnosis
Thymoma with megaesophagus and aspiration pneumonia.
Discussion
Thymoma and lymphoma are the two most common causes of cranial mediastinal masses in dogs. Thymoma is associated with myasthenia gravis in 40% of dogs and occasionally in cats. Thymoma is a tumor of the epithelial portion of the thymus, but often has a population of mature lymphocytes. In contrast, thymic lymphoma is comprised of less mature lymphoblasts. On radiographs and CT, lymphoma and thymoma look similar.
Roy ME, Wrigley R, Craft SL, et al. Radiographic prediction of the nature of cranial mediastinal masses in dogs. Journal of Small Animal Practice 2006;47:761-761.