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

In the last two decades, canine mammary cancer has played an important role in human breast cancer research. In many cases, there are various similarities between the biological and clinical features of canine breast cancer and female breast cancer. Clinical studies and evaluation of prognostic parameters of canine mammary cancer can increase confidence in generalizing results for human cancers. This study was performed in the direction of comparative oncology.

Clinical-pathological data from invasive type of canine mammary carcinoma were collected from clinical records and pathology reports. The parameters of 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.

97 patients were included in the study and the mean age was 10.06 ± 2.73 years. 51% of the left mammary glands were involved and pT2 tumor size was the most common. Lymph nodes were involved in 27% of patients and 43% of tumors were grade I. Statistical analysis showed no statistical relationship between tumor size and laterality with other clinico-pathological features. However, there was a statistically significant relationship between tumor size and tumor grade and the condition of lymph nodes, so that with increasing tumor size, tumor grade increased and the likelihood of lymph node involvement increased.

The results of this study are very similar to breast cancer in women and show that canine mammary carcinoma is a suitable model in comparative oncology research. Dogs live shorter than humans, so researchers can get the results of treatment and survival rate assessments faster in clinical trials. By observing ethical principles, dogs with breast cancer may replace phase I and II of human clinical trials in some types of cancer in the near future.