Long-term outcomes of dogs undergoing surgical resection of mast cell tumors and soft tissue sarcomas: A prospective 2-year-long study.

Abstract

Report clinical outcomes of dogs with surgically excised mast cell tumors (MCT) and soft tissue sarcomas (STS). Prospective clinical study. Fifty-three dogs with 52 MCT (50 low grade, 2 high grade) and 19 STS (12 grade I, 6 grade II, 1 grade III). All dogs were examined at 3, 6, 12, 18, and 24 months postoperatively, with cytologic or histopathologic evaluation of suspected local recurrences. Dogs euthanized because of study tumor-related causes underwent necropsy. Median intraoperative margins were 20 mm and 30 mm wide for MCT and STS, respectively, with 1 fascial plane resected en bloc. The narrowest histologic tumor-free margins measured <1 mm in 21 of 52 (40%) MCT and 7 of 19 (37%) STS. All dogs were followed for 24 months. Two of 50 (4%) low-grade MCT were diagnosed, with local recurrence 181 and 265 days postoperatively. Two of 36 (6%) dogs with low-grade MCT developed visceral metastasis 181 and 730 days postoperatively. One of 2 dogs with high-grade MCT developed local recurrence 115 days postoperatively. No local recurrence or metastasis was diagnosed after excision of 19 STS. Local recurrence rates among predominantly low- to intermediate-grade MCT and STS were low, despite a high prevalence of histologic tumor-free margins <1 mm. Surgical recommendations for high-grade tumors cannot be extrapolated from this population. Surgeons should seek to achieve microscopically complete excision for MCT and STS while minimizing patient morbidity and considering limitations of histopathology in predicting outcomes.