Abstract
Background:
Thymoma is the second most common mediastinal tumour in cats, and surgical excision is considered the treatment of choice. The median sternotomy is the most frequently used surgical approach. In contrast, although intercostal thoracotomy is widely employed in thoracic surgery (e.g., cardiac surgery or lung lobectomy), it has not been systematically reported in the context of feline thymoma. Herein, we report seven cases of feline thymoma treated via intercostal thoracotomy. We describe the tumour location (based on preoperative imaging), tumour diameter, choice of intercostal approach site, perioperative complications, and outcomes. To the best of our knowledge, this is the first case series to evaluate the feasibility and utility of intercostal thoracotomy for thymoma resection in cats.

Case Description:
Seven client-owned cats underwent intercostal thoracotomy for thymoma. Preoperative evaluation with computed tomography (CT) or thoracic ultrasonography revealed that the mass was located on the left side of the thoracic cavity when referenced to the midline defined by the sternum in all cases. The median tumour diameter was 5.2 cm (range, 4.0–6.4 cm), indicating relatively small masses. On the basis of these findings, a left fourth intercostal thoracotomy was performed in all cats. Postoperative complications included anemia that did not require transfusion in 2 cats and subcutaneous oedema in 3 cats. The duration of hospitalisation ranged from 3 to 4 days. One cat died 105 days postoperatively from a cause unrelated to thymoma, whereas the remaining 6 cats were alive at the last follow-up (105–850 days). No recurrence or metastasis was detected in any patient during the observation period.

Conclusion:
In this case series of 7 cats with thymoma, intercostal thoracotomy-associated complications were minor, and the postoperative course was favourable. These findings suggest that intercostal thoracotomy is an effective surgical approach for feline thymoma, particularly when the tumour is relatively small and predominantly located on one side of the thoracic cavity. In selected cases, intercostal thoracotomy may represent a viable alternative to median sternotomy.

Key words: Case series; Feline thymoma; Intercostal thoracotomy; Postoperative outcome; Surgical approach.