Thoracoscopic removal of cranial mediastinal masses in dogs is associated with a low conversion rate, excellent survival to discharge, and good long-term outcome.

Objective: To report the complications and outcomes associated with thoracoscopic cranial mediastinal mass resection in dogs.
Animals: 49 client-owned dogs that underwent thoracoscopic cranial mediastinal mass removal.
Methods: This was a retrospective cohort study (January 1, 2014, to July 31, 2023), and the medical records of 49 client-owned dogs that underwent thoracoscopic cranial mediastinal mass removal were reviewed. The signalment, history, clinicopathologic features, perioperative complications, and long-term outcome were recorded.
Results: Preoperative myasthenia gravis (MG) and megaesophagus (ME) were identified in 17 of 49 (35%) dogs and 11 of 49 (22%) dogs, respectively. The median maximal tumor diameter on CT images was 4.7 cm (range, 2.7 to 8.5 cm). Nonemergent conversion to an open procedure was necessary in 4 of 49 (8%) dogs, and dogs with conversion to an open procedure had a significantly larger median maximal CT tumor diameter than dogs without conversion (P = .03). The most common tumor type was thymoma (37/49 [76%]). The overall median survival time for dogs with thymoma was 1,102 days (95% CI, 482 to upper bound not reached). The median survival time for dogs with thymoma and concurrent presurgical MG was 182 days (95% CI, 14 to upper bound not reached). Presurgical diagnosis of MG (P = .44) or ME (P = .69) was not associated with survival time.
Clinical Relevance: Thoracoscopic removal of cranial mediastinal masses was associated with low conversion and complication rates. Long-term survival is possible, and thoracoscopic removal should be considered for select cases.