Portal site metastasis after thoracoscopic resection of a cranial mediastinal mass in a dog.

CASE DESCRIPTION

An 11-year-old castrated male Vizsla was evaluated for excision of a cranial mediastinal mass.

CLINICAL FINDINGS

The dog had a 1-month history of a cough that had recently increased in frequency. On physical examination, the dog had a grade 2/6 left systolic heart murmur and multiple subcutaneous masses. A soft tissue mass was observed in the cranioventral aspect of the thorax on radiographs. Results of a CT scan revealed a well-defined, 2.8 × 3.2 × 3.9-cm soft tissue mass in the cranial mediastinum.

TREATMENT AND OUTCOME

The dog underwent video-assisted thoracoscopic removal of the mediastinal mass and recovered routinely. Histologic examination of excised tissues revealed malignant thymoma. Approximately 6.5 months after surgery, the dog was evaluated because of polyuria, polydipsia, decreased appetite, and vomiting. On physical examination, masses were found in both axillary regions. Results of serum biochemical analysis indicated hypercalcemia. Thoracic ultrasonography revealed pulmonary metastases and a large mass in the right caudoventral region of the thorax. The dog received supportive care and medical treatment for hypercalcemia, but clinical signs recurred. Euthanasia was elected; necropsy and histologic examination revealed thymic carcinoma.

CONCLUSIONS AND CLINICAL RELEVANCE

Descriptions of the development of portal site metastasis in canine patients are rare. In this patient, portal site metastasis developed rapidly after thoracoscopic resection of a malignant thymic mass and was associated with hypercalcemia. As use of thoracoscopic procedures increases in veterinary medicine, it will be important to monitor the development of major complications such as those in the patient of this report.