Immunocytochemistry of myoepithelial cell types in canine mammary tumors.

Myoepithelial cells (MECs) are known to play an active role in mixed mammary tumors and are found in dogs as well as in humans. The study aimed to assess the morphologic features of epithelial and mesenchymal cells and MECs and investigate their roles in epithelial-mesenchymal transformation in different tumor types in canine mammary tumors. Immunohistochemical staining was performed on 165 specimens from benign mixed tumors (BMT), carcinosarcomas, and simple carcinomas (SC). Double immunohistochemical staining was for the antigen pairs p63/actin, p63/vimentin, p63/CK19, p63/CK8, p63/CK14. BMP6 was demonstrated only by single immunostaining. For BMP6, epithelial cells were positive in BMTs, carcinosarcomas, and SCs. Myoepithelial cells were variably positive for p63, actin, vimentin, and CK14. Epithelial cells were usually positive for CK19 and CK8. MECs include both epithelial and mesenchymal components, so metaplasia in epithelial cells can also form in MECs, and these two cell types should be evaluated together.