Immunohistochemical Expression of Caveolin-1 in Normal and Neoplastic Canine Mammary Tissue

Caveolins are the major structural proteins of caveolae and play a role in tumour surveillance. The expression of caveolin-1 (Cav-1) was investigated immunohistochemically in samples of normal canine mammary tissue (n = 5), benign (n = 23) and malignant (n = 45) mammary tumours, tumour emboli (n = 10) and metastatic lesions (n = 10). Cav-1 was not expressed by normal luminal epithelium, but was consistently expressed by normal myoepithelial cells. There was no epithelial expression of Cav-1 by the benign mammary lesions, but the molecule was detected in 35.6% of the malignant lesions, 80% of the tumour emboli and in 40% of the metastatic lesions. These findings link increased expression of Cav-1 to neoplastic transformation and suggest that Cav-1 expression is associated with more malignant canine mammary tumours and their vascular invasion and regional lymph node metastasis.