Clinical outcome of cutaneous mast cell tumors in dogs

A prospective study was performed on 15 client-owned dogs to assess the clinical outcome after surgical excision of canine cutaneous mast cell tumors (MCTs) depending on histologic grade and completeness of surgical margins. The surgical margins were evaluated as complete, close or incomplete if they were more than 3 mm, from 1 to 3 mm or less than 1 mm wide, respectively. Survival time for dogs with low grade MCT (based on grading by M. Kiupel et al.) was 409 days compared with only 60 days for dogs with high grade tumor. Dogs with high grade tumors had significantly shorter survival time and worse prognosis than dogs with low grade tumors (p=0.013). Complete excision was associated with lower possibility and longer time to tumor recurrence, as well as longer survival, however, marginal surgical border status did not have a significant impact on time to tumor recurrence and survival. It was also found that tumor duration but not tumor size had a significant impact on surgical margin status (p=0.047). Tumor size significantly affected survival time with larger tumors being correlated with shorter survival (p=0.03). The results of our study suggest that grade, tumor size and recurrence are significant factors for MCT prognostication.