CLINICOPATHOLOGICAL AND IMMUNOHISTOCHEMICAL EVALUATION OF MAMMARY TUMOURS IN INTACT FEMALE DOGS

Abstract

Canine mammary tumors (CMTs) are among those most frequently diagnosed in intact female dogs. They share biological and hormonal similarities with human breast cancer, which renders them valuable models in comparative oncology. This study aimed to evaluate the clinical, histopathological, and immunohistochemical characteristics of CMTs in intact female dogs. A total of 22 archived CMT cases submitted between 2013 and 2023 was conducted at the Federal University of Agriculture, Abeokuta. Samples were obtained through mastectomy or nodulectomy from female dogs presented at private veterinary clinics and a teaching hospital. Clinical data, including age, tumour size, location, lymph node involvement, and spay status, were recorded. Most dogs were German Shepherds (45.5%) with a mean age of 8.15 years; none were spayed. The tumours were predominantly malignant (77.3%) and commonly located in the inguinal mammary glands (40.9%). Stage T2 (45.5%) and histological grade II (72.7%) were the most prevalent. E-cadherin was immunopositive in 89% of tumours, with stronger expression in malignant cases. N-cadherin expression was significantly associated with malignancy (p = 0.001), indicating epithelial-mesenchymal transition (EMT). Oestrogen receptors α (Orα) was strongly expressed in all tumours, with significantly higher levels in cases of malignancy (p = 0.002). Progesterone receptor (PR) and vimentin were observed only in malignant tumours, while Ki-67 showed mild, non-significant expression. These findings suggest that N-cadherin, ORα, and PR may serve as potential biomarkers of malignancy and hormonal responsiveness in CMTs. They also support the relevance of molecular profiling in the diagnosis and management of canine mammary tumours.