Detection of cell origin by immunohistochemistry in canine mammary tumours

The main objective of this study was to improve the tumour type diagnosis using immunohistochemical markers for epithelial (cytokeratins AE1/AE3) and myoepithelial cells (cytokeratins AE1/AE3, calponin, alpha-smooth muscle actin (alpha-SMA)) and for mesenchymal components (vimentin) in the case of canine mammary tumours. Tumours were obtained from 43 female dogs in different ages and breeds and were classified according to WHO-AFIP after histopathological examination. The tumours were diagnosed as in situ carcinoma (3 cases), complex carcinoma (12 cases), tubulopapillary carcinoma (12 cases), solid carcinoma (1 case), spindle cell carcinoma (1 case) and carcinosarcoma (14 cases). Cytokeratins AE1/AE3 were expressed in all cases except in the spindle cell carcinoma and vimentin was expressed by mesenchymal cells in all cases except in the in situ carcinoma whereas alpha-SMA and calponin were specifically detected in complex carcinoma and in carcinosarcoma (88.5% and 69.2%, respectively). However, calponin immunostaining was generally moderate to strong whereas the alpha-SMA detection remained often weak. These results emphasize the interest of immunohistochemical markers for identify the tumoural cell origin in canine mammary tumours.