Assessment of prognostic factors in dogs with mammary gland tumors: 60 cases (2014-2020)

Canine mammary gland tumors are the most common neoplasms in intact female dogs. Approximately half of all mammary tumors are malignant, and there is a risk of metastasis, which is associated with a poor prognosis. This study was to evaluate the prognostic factors of canine mammary gland tumors and the risk factors associated with the development of malignant tumors. From 2014 to 2020, 60 dogs with mammary gland tumors that underwent surgical treatment were evaluated in this retrospective study. Tumor size, TNM stage, and histopathological results were prognostic factors for 2-year survival after surgery. Every 10 mm increase in tumor size, increased the risk of death within 2 years after surgery 1.213 times. Dogs with TNM stage IV or V had 8.667 fold risk of death within 2 years after surgery. The 2-year survival rate for dogs with benign tumors was 90.2% and for malignant tumors was 67.3%. Tumor size is the most important prognostic factor for canine mammary gland tumors. As tumor size increased by 10 mm, the risk for development of malignant tumors increased by 1.487 times. Tumors larger than 30 mm are highly likely to be malignant, and metastatic evaluation and wide resection should be considered.