Cutaneous mast cell tumors in dogs: Association with gonadectomy

A retrospective case-control study was conducted using the clinical records of dogs treated at the Veterinary Teaching Hospital of Uruguay between 2017 and 2022 with a confirmed diagnosis of cutaneous mast cell tumor (MCT). A total of 141 affected dogs were compared with a randomly selected control group of 141 dogs without cutaneous tumors that attended the hospital during the same period. The association between gonadectomy and cutaneous MCT was evaluated by estimating crude and sex- and age-adjusted odds ratios (ORs) using univariate and multivariable logistic regression models. Overall, gonadectomy was associated with lower odds of cutaneous MCT. However, effect modification by sex was detected in the association between gonadectomy and MCT (p-interaction = 0.04). Sex-stratified analyses showed that gonadectomy was significantly associated with lower odds of MCT in males (OR = 0.16, 95% confidence interval [CI], 0.06-0.41), whereas the association in females was weaker and not statistically significant (OR = 0.56, 95% CI, 0.25-1.27). In addition, dogs aged ≥7 years had substantially higher odds of MCT than adult dogs aged 2-6 years. These findings suggest that the association between reproductive status and cutaneous MCT is complex and may differ by sex. However, given the observational nature of the case-control design, the results should not be interpreted as evidence of a causal relationship. Further prospective studies, particularly those evaluating the timing of gonadectomy, are warranted.