LAUSR

In canine cutaneous mast cell tumors (cMCTs), histologic grade and clinical stage are the most important prognostic factors, with high-grade tumors and metastatic lymph nodes (LNs) significantly influencing the evolution of disease. However, it is uncertain whether histologic grade and clinical stage should be given equal weighting value in patient prognostication and management. Dogs with low- and high-grade cMCTs and at least one overtly metastatic sentinel LN undergoing standardized treatment, consisting of surgical excision of the cMCT, lymphadenectomy and chemotherapy, were retrospectively included. The aim was to determine whether, at the same clinical stage, histologic grade retained prognostic relevance. Sixty dogs were included: 26 had a high-grade cMCT tumor and 34 had a low-grade cMCT. Median follow-up was 367 days (range, 187-748) in the high-grade group, and 1208 days (range, 180-2576) in the low-grade group. Median time to progression was significantly shorter in the high-grade group than in the low-grade group (214 days versus not reached; P<0.001), as well as tumor-specific survival (545 days versus not reached; P<0.001). On multivariable analysis, a high histologic grade and incomplete margins retained prognostic significance for both tumor progression and tumor-specific death. In dogs with cMCT and at least one overtly metastatic LN undergoing multimodal treatment, histologic grade significantly correlated with outcome. Overall prognosis was not unfavorable, even in the high-grade group, further supporting that a multimodal therapeutic approach, addressing primary tumor and sentinel LN, should be offered. Whether chemotherapy should be incorporated in the therapeutic planning of low-grade cMCTs remains to be defined. This article is protected by copyright. All rights reserved.