IMMUNOHISTOCHEMISTRY WITH KERATIN, VIMENTIN, DESMIN, AND ALPHA-SMOOTHMUSCLE ACTIN MONOCLONAL-ANTIBODIES IN CANINE MAMMARY-GLAND - BENIGN MAMMARY-TUMORS AND DUCT ECTASIAS

Duct ectasias (n=2) and different types of benign canine mammary tumou rs (n=19) were studied immunohistochemically with monoclonal antibodie s (MoAbs) directed against various human keratin types (K), alpha-smoo th muscle actin, vimentin, and desmin. In the duct ectasias and in mos t tumours the epithelial structures revealed an inner and outer cell l ayer. The inner cell layer was characterized by labelling with K 7, 8, 18, 19 and mostly also with K 4 and/or K 10 MoAbs. The outer cell lay er was almost invariably labelled by K 14, K 14 and 17, and a-smooth m uscle actin MoAbs. The labelling patterns of both duct ectasias and tu mours corresponded largely to the patterns observed in normal mammary gland tissue, although a more distinct heterogeneity was seen. Tumours histomorphologically assumed to be of a myoepithelial origin did not show immunohistochemical features of myoepithelial cells. The myoepith elial nature of the vast majority of spindle-shaped cells present in t he adenomas of the complex type and in the fibroadenomas of the benign mixed type could not be confirmed immunohistochemically. These cells, however, unequivocally expressed vimentin, suggesting proliferation o f stromal cells in these tumours, which in the fibroadenomas of the be nign mixed type may show metaplasia to bone or cartilage. In the duct ectasias and in some tumours, a fraction of elongated stromal cells, p robably representing myofibroblasts, was labelled with the alpha-smoot h muscle actin MoAb.