Immunohistochemical Evaluation of BRCA1 and BRCA2 Expressions in Dogs with Different Grades of Malignancy, Histological Subtypes and Metastatic/Non-Metastatic Mammary Gland Adenocarcinomas

This study primarily aimed to examine BRCA1 and BRCA2 expression in various types of canine mammary gland adenocarcinomas using immunohistochemistry with the avidin-biotin-peroxidase Complex (ABC).The study material comprised adenocarcinoma samples obtained from the mammary glands of 20 dogs that were presented for routine histopathological examination at the Department of Pathology in the Faculty of Veterinary Medicine at Kafkas University between 2012 and 2022.The tumour masses had a highly haemorrhagic and ulcerative appearance.These round or oval-shaped masses were primarily greyish-white in colour.Especially in mixed-type carcinomas, tumour masses were particularly firm in consistency due to the presence of bone and cartilage components.5 out of 20 cases (25%) were classified as mixed-type carcinoma, 4 out of 20 cases (20%) as tubular-type carcinoma, 4 out of 20 cases (20%) as solid-type carcinoma, 3 out of 20 cases (15%) as tubulopapillary-type carcinoma, 3 out of 20 cases (15%) as intraductal papillarytype carcinoma and 1 out of 20 cases (5%) as micropapillary-type carcinoma.6 cases were classified as grade-1 malignancy (30%), 6 as grade 2 (30%), and the remaining 8 as grade 3 (40%).Metastatic tumour foci in the lung and lymph nodes were also confirmed by histopathology.No difference was observed between the degree of differentiation of secondary and primary tumour foci.BRCA1-and BRCA2-positive immunolabelling were predominantly concentrated in the cytoplasm of tumour cells.Compared to metastatic cases, the immunopositivity for the aforementioned biomarkers was significantly more intense in non-metastatic cases.However, BRCA1 and BRCA2 immunoreactivities were significantly higher in early-grade cases than in advanced-grade cases.Although an ideal biomarker for canine mammary gland tumours has yet to be identified, immunohistochemical data obtained from the current study on BRCA1 and BRCA2 are considered important and useful biomarkers for determining malignancy grade, prognosis, and metastatic capacity in canine mammary gland adenocarcinomas.