Vet. Path. 11: 172-180 (1974) Malignant Thymoma with Metastases in a Dog

Abstract. An 8-year-old male Wire-Haired Fox Terrier with respiratory distress and cough had a malignant thymoma that had metastasised to the lungs, spleen, liver, dia-phragm, bronchial and mediastinal nodes, and pericardium by transcoelomic, vascular, and lymphatic routes. Myasthenia gravis, which occurs in some human patients with thymoma, was not evident. There are few reports of true thymomas in dogs [5]. TALERMAN and GWYNN [6] described one case and in a review of the literature found only five cases. WATSON and FARROW [8] and HALLet al. [2] have since reported one case each. All the reported thymomas were benign with no evidence of metas-tasis. A case of a malignant thymoma in a dog in which there was infiltration of tissue with transcoelomic and embolic spread is described. Case Report An 8-year-old male Wire-Haired Fox Terrier had respiratory distress and cough. Rectal temperature was normal. Antibiotics were administered, but 3 days later the animal's condition had deteriorated, and percussion of the chest showed abnormal solidity on the right side. Although the left side retained resonance, rales were heard on ausculta-tion. The dog died under anaesthesia prior to radiography. Pathology Both pleural cavities contained a moderate quantity of watery blood-stained fluid. A pale, fairly firm nodular mass, 8 X 6 X 6 em, containing areas of haemorrhage and brown discolouration was in the anterior mediastinum, and a similar mass, 6 X 3 X 3 em, was in the posterior mediastinum (fig. 1)