A Study on the Relationship Between Tumor Size, Tumor Grade and Lymph Node Involvement in Canine Mammary Cancer: Simulation of Tumor Behavior in Human Breast Cancer

Background: In the last two decades, canine mammary cancer has played an essential role in human breast cancer research. There are various similarities between biological and clinical features of canine breast cancer and female breast cancer in many cases. Clinical studies and evaluation of prognostic factors in canine mammary cancer can increase reliability in generalizing results to human cancers. This study was performed in the direction of comparative oncology. Methods: We collected clinicopathological data of an invasive type of canine mammary carcinoma from clinical records and pathology reports. Age, tumor laterality, tumor size, lymph node status, and tumor grade were recorded, and the relationships between the parameters were evaluated using linear regression analysis. Results: Ninety-seven patients were included in the study, and the mean age was 10.06 ± 2.73 years. The left mammary gland was involved in 51% of cases, and pT2 was the most common tumor size. Lymph nodes were involved in 27% of patients, and 43% of tumors were grade I. Statistical analysis showed no relationship between tumor size and laterality with other clinicopathological features. However, there was a statistically significant relationship between tumor size and tumor grade, and lymph node status. As the tumor size increased, tumor grade and the risk of lymph node involvement raised. Conclusion: Similar results of this study to breast cancer in women show that canine mammary carcinoma is a suitable model in comparative oncology research. Dogs live shorter than humans so that researchers can get the results of treatment and perform survival rate assessments faster in clinical trials. By considering ethical principles, dogs with breast cancer may replace phases I and II of human clinical trials in some cancer types soon.