Medical Management of a Cervical Thymoma by Radiation Therapy in an Indian Ringneck Parakeet (Psittacula krameri).

Thymomas are uncommon in birds and management is challenging because of tumor characteristics such as growth location and local invasiveness, limiting surgical and chemotherapeutic options. A 20-year-old female Indian ringneck parakeet (Psittacula krameri) was referred for radiation therapy because of an increase in size of a right-sided cervical mass. The mass was tentatively diagnosed as a thymoma after biopsy and incomplete surgical resection 3 months previously. Therapeutic management in this parakeet included 10 treatments of palliative radiation therapy over the course of 1 month. The tumor decreased in size by approximately 60% in length and 40% in width and was palpably softer after radiation therapy, but regrowth was observed 73 days after the final radiation treatment. One dose of chemotherapy with cyclophosphamide was administered at that time, but euthanasia was elected 5 days later due to the parakeet's declining clinical condition and poor prognosis. Radiation therapy was effective in this bird as a palliative treatment in reducing tumor size; however, a modified protocol or a multimodal approach may be needed for longer-term control of thymomas in avian species.