Clinical outcome for MCTs of canine pinnae treated with surgical excision (2004-2008)

Canine mast cell tumors (MCTs) are the most common cutaneous neoplasm in the dog. It has been suggested that MCT in certain locations may behave in a more biologically aggressive fashion than MCTs located in others; however, no published data are available for MCTs of canine pinnae treated with surgical excision. A retrospective study of 28 animals with surgical excision of MCTs of pinnae was completed with a medical record review and follow-up questionnaire to the operating veterinarian. The effect of tumor grade, clean or dirty excision, cartilage penetration, and mitotic index (MI) on local recurrence and survival time (ST) was evaluated. There was local recurrence in one dog with a grade 2 MCT and in seven of eight dogs with grade 3 MCTs. The median ST of animals with grade 1 and 2 MCTs was not reached, whereas the median ST of animals with grade 3 MCTs was 10 mo. There was no statistical association between histologically clean and dirty margins and either local recurrence or ST. A prolonged disease free interval without local recurrence may be achieved with local excision of grade 1 and 2 MCTs. Animals with grade 3 MCTs had a uniformly poor outcome with short times to local recurrence and death.