A 10-year-old female red panda (Ailurus fulgens styani) was diagnosed with a cranial mediastinal mass during routine annual physical examination. She exhibited no clinical signs of disease, and physical exam findings were unremarkable. Routine diagnostics performed included radiographs, complete blood cell count, serum biochemistry, heartworm antigen test, urinalysis, and abdominal ultrasound. The mass was noted on thoracic radiographs and located cranial and ventral to the heart. The results from the remaining diagnostics were unremarkable.
Thoracic ultrasound revealed a 5x3.5x3.3-cm mass. A fine-needle aspirate was performed, and approximately 60 ml of brownish-yellow fluid was collected and submitted for culture and cytology. Aerobic and anaerobic culture yielded no growth, and cytology of the aspirate was suggestive of thymoma. Further diagnostics were performed over a 2-month period and included radiographs, ultrasound, hematology, additional fine-needle aspirates, and computed tomography. CT revealed the mass to be closely associated with the heart, causing slight displacement, but no evidence of metastasis. During this time period, the mass had increased in size to 5.1x3.7x8.7 cm. A median sternotomy was performed, and the entire mass was removed without complication. Histopathology identified the mass as a benign thymoma. The panda recovered without complication and has had no evidence of tumor recurrence for 2 years.