VCS/ACVP Oncology-Pathology Working Group Summary and Subgroup Recommendation for Grading of Canine Cutaneous Mast Cell Tumors Species/Tumor: CANINE CUTANEOUS MAST CELL TUMOR SUBGROUP

Introduction: The cornerstone for the prognosis of canine cutaneous mast cell tumor has been the histological grade. A critical appraisal of the available literature can help pathologists and clinicians better understand the values and limitations of histological grading. The first consensus document of the OPWG on the histological grading of cutaneous mast cell tumors was divulgated in 2013. Since then, some key manuscripts have been published expanding and improving our knowledge on the subject. Some studies validated the use of the two-tier grading system and other supported the prognostic value of the mitotic index. A new innovative field is the development of cytological grade and we report the initial findings. This current document takes into account new and relevant literature since the time of the initial document (2013) to ensure currency of the VCS/ACVP OPWG consensus on the topic of CCMCT. Similarly, it is expected this document will be updated regularly as additional research and associated data come to light.