Immunohistochemical Reactivity of Basal and Luminal Epithelium-specific Cytokeratin Antibodies within Normal and Neoplastic Canine Mammary Glands

Human basal epithelium (myoepithelium)-specific (312C8–1) and luminal epithelium-specific (13H5) cytokeratin antibodies were applied to frozen sections of normal canine mammary tissues (seven), benign adenomas and hyperplasias (five), mixed tumors (12), and adenocarcinomas (18) to determine if epithelial subsets could be discriminated by the use of an avidin biotin peroxidase complex immunohistochemical procedure. The 312C8–1 and 13H5 antibodies were consistently reactive with basal and luminal epithelium, respectively, in the normal mammary gland (7/7) and in benign adenomas and hyperplasias (5/5). Mixed mammary tumors had similar basal and luminal epithelial reactivity and also had proliferating spindle-shaped stromal cells that were reactive with 312C8–1 (10/12) and 13H5 (4/12). The adenocarcinomas were subclassified into basal, luminal, and basal/luminal on the basis of 312C8–1 reactivity (4/18), 13H5 reactivity (2/18), and dual reactivity with mutually exclusive anatomic distribution (11/18), respectively. Those tumors with dual immunoreactivity were indicative of noninvasive carcinomas. Dogs with neoplasms that were reactive with 312C8–1 and nonreactive with 13H5 had local recurrence or distant metastasis within 2 weeks to 6 months after diagnosis. Other antibodies used for comparison were pan cytokeratin AE1/AE3, actin HHF35, and vimentin. 312C8–1 and 13H5 antibodies are specific for canine mammary basal and luminal epithelium, respectively, and by employing these antibodies, the origin and differentiation of canine mammary neoplasms can be determined more accurately than on the basis of hematoxylin and eosin-stained tissue alone.