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.