Minimally Invasive Thymoma Surgery in Cats: New Evidence from a 17-Case Thoracoscopic Study

Thoracoscopic Resection of Cranial Mediastinal Masses: Retrospective Study in 17 Cats

Stefania Renier, Federico Massari, Manuel Jimenez Pelaez, Angelo Tapia-Araya, Vincenzo Montinaro, Felipe J. Lillo-Araya, Roberto Properzi, Filippo Cinti

Background

Cranial mediastinal masses in cats are uncommon, with thymic lymphoma and thymoma representing the most frequent diagnoses. Optimal management depends on accurate characterization through imaging and cytology to determine whether medical therapy or surgical excision is indicated. Traditional surgical approaches rely on median sternotomy or thoracotomy, though thoracoscopy may reduce morbidity. Prior to this study, only a single feline case report described thoracoscopic removal of a cranial mediastinal mass. This retrospective study aimed to determine the feasibility, complications, and outcomes associated with thoracoscopic resection in a larger feline cohort.

Methods

Medical records from seven veterinary institutions (2019–2024) were reviewed for cats undergoing attempted thoracoscopic resection of cranial mediastinal masses. Inclusion required an initial thoracoscopic attempt, adequate surgical and anesthetic records, and at least one postoperative follow-up. Data included signalment, diagnostics (CT, radiography, cytology), anesthetic and surgical details, tumor measurements, complications, and short- and long-term outcomes. Tumor size was assessed via preoperative imaging or postoperative specimen measurements. Complications were classified as minor or major, and conversions to open procedures were documented along with their indications.

Results

Seventeen cats were included, most commonly Domestic Shorthairs (88.23%). Dyspnea was the predominant clinical sign (58.82%). CT was performed in 94.12% of cats, and FNA cytology was diagnostic in 94%. Thymoma was the most frequent histopathologic diagnosis (70.6%). Thoracoscopy was initiated in all cats; however, 6/17 (35.29%) required non-emergent conversion to open or video-assisted approaches, often when masses exceeded 5 cm or when adhesions limited visualization or working space. Median surgical time was 50 minutes, and all cats survived the perioperative period. Short-term complications were minor (seromas or pleural effusion). Mean survival time was 390.62 days, with no reported tumor recurrence or port-site metastasis.

Limitations

The retrospective design limited standardization of surgical technique, port placement, and anesthetic protocols. Volumetric tumor analysis was not possible for all cases. The influence of one-lung ventilation could not be assessed. Follow-up duration varied, preventing uniform long-term outcome assessment.

Conclusions

Thoracoscopic resection of cranial mediastinal masses in cats is feasible and associated with low morbidity and favorable outcomes. Larger tumors (>5 cm) and adhesions increase the likelihood of conversion to open or video-assisted procedures. Careful case selection — prioritizing masses without vascular invasion and ≤5 cm diameter — may reduce conversion rates. Thoracoscopy offers a minimally invasive alternative to sternotomy when anatomical constraints allow.

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