Prognostic significance of immunohistochemical markers and histological classification in malignant canine mammary tumors.

Canine mammary carcinoma represents a model for the study of human breast cancer, although the prognostic value of various clinical, histological and immunohistochemical parameters has shown contradictory results. A prospective study, through a 4-year follow-up, was performed in 77 patients with mammary carcinoma to analyze the association between histological diagnosis, grade of malignancy, peritumoral and vascular invasion. We have also performed immunohistochemistry for the expression of ER, PR and HER2 and COX-2 that define human biomarkers of disease progression and treatment response. An association between histological diagnosis and clinical stage was observed with a high proportion of complex carcinoma classified as stage I. There was a higher proportion of ER+/PR+/HER2- tumors in stage I. In contrast, triple-negative tumors (ER-/PR-/HER2-) were found mainly in advanced clinical stages and were associated with vascular and peritumoral invasion. The tumors included in group VII (carcinosarcoma/adenosquamous carcinoma/other special types of carcinoma) had a higher expression of COX-2. The univariate analysis showed that those patients with complex carcinoma had the lowest incidence of metastases and the highest probability of survival. In contrast, a high proportion of patients with anaplastic/inflammatory carcinoma developed metastases and showed the lowest probability of survival. In addition, the estimated survival time was shorter for those patients with triple-negative tumors and those with high COX-2 expression. However, in the multivariate analysis, only the peritumoral invasion maintained its prognostic significance. In conclusion, in our study anaplastic/inflammatory carcinomas had the worst prognosis with a high proportion of triple negative tumors in this category. This article is protected by copyright. All rights reserved.