CLINICOPATHOLOGICAL SIGNIFICANCE OF CASPASE-3 AND KI-67 EXPRESSION IN CANINE MAMMARY GLAND TUMOURS

Fifty canine mammary gland tumours (CMGT) (18 benign and 32 malignant) were studied by immunohistochemical detection of active caspase-3 and Ki-67 antigens in order to determine their association with several clinicopathological parameters. The percentage of caspase-3 positive cells was significantly higher in benign tumours as compared to their malignant counterparts (P = 0.001). In the group of malignant tumours there was no significant association between active caspase-3 and the clinicopathological variables considered. The percentage of Ki-67 positive cells was significantly higher in malignant tumours compared to the benign ones (P = 0.001). In the group of malignant tumours, Ki-67 expression showed a statistically significant association with tumour size (P = 0.025), histological type (P = 0.010), mitotic grade (P = 0.001), nuclear grade (P = 0.025), differentiation grade (P = 0.004), histological grade of malignancy (P = 0.002), and presence of metastases in regional lymph nodes (P = 0.025). Furthermore, this study revealed a negative correlation between the percentages of active caspase-3 and Ki-67 (r = -0.39; P = 0.04). Thus, our results suggest a loss of balance between cell death and cell division in CMGT.