Cell Proliferation Study in Canine Mammary Carcinomas

Prognosis of postsurgical behaviour of mammary carcinomas in dogs is difficult using a routine histopathological examination alone. The aim of the present study was an assessment of prognostic value of proliferating cell nuclear antigen (PCNA) and Ki-67 antigen expression in canine mammary carcinomas. Expression was evaluated with computer assisted microscopic image analysis in surgically removed, formalin-fixed, paraffin-embedded tissue samples by means of immunohistochemistry. The growth fraction parameters were compared with previously described data of flow cytometric DNA analysis as well as with clinical outcome based on 24-month long postoperative observation and careful postmortem examinations. In the group of dogs which died or were euthanatized due to metastases the mean Ki-67 index value was significantly higher in comparison to the group of animals which survived the observation period without malignant process progression. Such a relation was not observed for PCNA. Both Ki-67 and PCNA index values were significantly higher in the group of dogs with neoplasms that had increased levels of cells in the S-phase. The presence of a significant correlation between the Ki-67 antigen index and the clinical course after the operation, calculated using the t-student test, with the lack of such correlation in variance analysis test suggests that it should be treated only as a prognostic marker helper. The heterogenity of staining of the cell nuclei and the lack of correlations with the clinical course in case of PCNA seems to disqualify it as a prognostic factor.