Exploring canine mast cell tumors: An investigation into demographic characteristics, and grading system analysis from a pathology lab data (2019–2021)

Mast cell tumors (MCT) are among the most common neoplasia in dogs, representing up to 21 % of skin tumors. However, etiology and risk factors for its development remain unclear. This study aimed to reduce this knowledge gap by comprehensively analyzing 905 MCT cases diagnosed in Portugal between 2019 and 2021, using descriptive and inferential analyses. Most tumors affected the skin, with 69.9 % and 21.2 % classified as cutaneous and subcutaneous tumors, respectively. Only subcutaneous MCT exhibited female predisposition. Breed-specific analyses revealed male predominance in French Bulldogs and female predominance in Shar-Peis. Tumors in the extremities were the most prevalent (43.2 %, n = 183). Age-related characteristics varied by breed, with Pugs, Boxers, French Bulldogs, and Shar-Peis being diagnosed at younger ages. Logistic regression showed that age increased the likelihood of developing higher-grade cutaneous tumors (p < 0.01, OR=1.17, 95 % CI 1.02–1.21) and subcutaneous tumors with an infiltrative pattern (p = 0.02, OR=1.17, 95 % CI: 1.04 –1.33). The estimated annual incidence risk for MCT in dogs from Lisbon and Setúbal districts is 3.1 cases per 10,000 dogs, and 3.0 for males and 3.2 for females. Compared to mixed-breed dogs, Boxers, Shar-Peis, and Golden Retrievers had significantly higher relative risks (7.1, 6.3, and 5.9, respectively, p < 0.01). Sex-specific relative risks showed Boxers with the highest values among males (9.9, p < 0.01) and Shar-Peis among females (8.0, p < 0.01). This study provides insights into canine MCT, emphasizing the importance of age, sex, and breed, as well as the need for tailored veterinary care that considers these demographic characteristics to enhance prevention, early detection, and management.