Outcome of dogs with mast cell tumors in the inguinal or perineal region versus other cutaneous locations: 124 cases (1990-2001)

OBJECTIVE: To compare clinical outcome of dogs with cutaneous mast cell tumors (MCTs) in the inguinal or perineal region with outcome for dogs with MCTs in other cutaneous locations. DESIGN: Retrospective study. ANIMALS: 37 dogs with MCTs in the inguinal or perineal region and 87 dogs with MCTs in other cutaneous locations. PROCEDURE: Information obtained from the medical records included sex, breed, age, histologic grade of all tumors, number and location of all tumors, tumor size (ie, diameter of the tumor), completeness of surgical excision, treatments administered in addition to surgery, and outcome. In all dogs, the primary treatment consisted of surgical excision. RESULTS: Disease-free interval and survival time for dogs with MCTs in the inguinal or perineal region were not significantly different from values for dogs with MCTs in other cutaneous locations. Dogs with incompletely excised tumors, dogs with grade III tumors, and dogs that received systemic treatment were 2, 2.5, and 4 times as likely, respectively, to have a relapse. Factors significantly associated with a shorter survival time were age > 8 years, metastatic disease at the time of initial diagnosis, and tumor relapse. CONCLUSIONS AND CLINICAL RELEVANCE: Results of the present study suggest that dogs with MCTs in the inguinal or perineal region do not have a worse prognosis in regard to disease-free interval or survival time than do dogs with MCTs in other cutaneous locations. Treatment recommendations for dogs with cutaneous MCTs should be based on confirmed predictors of biological behavior, such as histologic grade and clinical stage.