Pathology of triple negative basal like mammary tumour in a male non-descript dog - Case report

Triple negative basal like carcinoma is a rare and aggressive variant of a malignant mammary tumor in male dogs. The present work was conducted on 46 clinical cases suspected for canine mammary tumours collected over a period of 2 years. Out of 46 cases diagnosed as mammary tumour, one case was found in an 11-year-old male non-descript dog. Clinical examination revealed firm, ulcerated mass in the right caudal abdominal mammary gland. Cytological examination revealed clusters of malignant epithelial cells, few spindle cells and necrotic debris with admixture of inflammatory cells. Histologically, the tumour was confirmed as carcinosarcoma composed of adenocarcinoma with solid sheets, tubular, acinar pattern and spindle shaped cells in solid sheets. Immunohistochemistry revealed that the tumour was negative for Her2, ER, PR, but positive for CK5/6 and vimentin. Vimentin differentiated the epithelial components from mesenchymal tissue. Based on the gross, histopathological and immunohistochemical features, ulcerated mass in the right caudal abdominal mammary gland of the male non-descript dog was diagnosed as triple negative basal like mammary tumor.