Introduction

Mammary tumor is the most important neoplasm in intact female dogs. Mutations in p53 tumor suppressor gene lead to overexpression of p53 protein in mammary neoplasms and have been associated with a worse prognosis in women, but its prognostic value in canine mammary tumors (CMT) is controversial.

Objectives

In the current study we evaluate the p53 expression in CMT and verify its correlation with tumor features and overall survival (OS); we also evaluate the disease-free interval (DFI) and tumor development interval in the mammary gland remnant (TDIMG) of bitches submitted to partial mastectomy.

Methods

One hundred bitches were followed up for a minimum of two years. Determination of p53 expression was performed by immunohistochemistry using the streptavidin-biotin-peroxidase technique. Samples with more than 10% of labeled neoplastic cells were considered positive, and percentage and marking intensity were evaluated.

Results

p53 overexpression was observed in 65% (65/100) of the tumors. There was a correlation between p53 overexpression and histological subtype, which was higher in tubular and complex carcinomas (p=0.017), and a higher marker score and higher labeling intensity were observed in high histological grade. However, there was no correlation between p53 expression and DFI (p=0.441) and TDIMG (p=0.240). The age of the dog at diagnosis was a factor that also influenced OS, being worse in bitches with more than eight years (p=0.023).

Conclusions

This study demonstrated that the p53 overexpression in CMT should be considered as an important prognostic factor, related to a worse survival.