Immunohistochemical assay for detecting estrogen receptors in canine mammary tumors.

TitleImmunohistochemical assay for detecting estrogen receptors in canine mammary tumors.
Publication TypeJournal Article
Year of Publication1999
AuthorsGraham JC, O'Keefe DA, Gelberg HB
JournalAmerican journal of veterinary research
Date Published1999 May
KeywordsAnimals, Cell Nucleus, Dog Diseases, Dogs, Female, Immunohistochemistry, Male, Mammary Neoplasms, Animal, Receptors, Estrogen

OBJECTIVE: To determine the estrogen receptor (ER) content of canine mammary gland tumors by use of immunohistochemical (IHC) examination of formalin-fixed sections.

SAMPLE POPULATION: 21 mammary gland tumors from 20 adult dogs.

PROCEDURE: ER were detected in formalin-fixed tissues, using an avidin-biotin alkaline phosphatase IHC assay and were quantified on fresh-frozen tumor samples, using a modified dextran-coated charcoal (DCC) assay.

RESULTS: 7 of 21 tumors had visually detectable nuclear ER by use of IHC staining, whereas 8 of 21 tumors were positive for ER by use of the DCC assay. The ER-positive cells in 5 IHC-positive tumors were epithelial cells with histologic criteria of early malignancy. The remaining 2 ER-positive tumors detected by use of IHC had ER-positive mast cells within areas of connective tissue around the tumor.

CONCLUSIONS: Immunohistochemistry is an additional method for detection of ER in canine mammary tumors. The major advantage of this type of assay is that it may be performed on formalin-fixed tissues, and individual ER-positive cells may be identified. Discovery of ER-positive mast cells by use of IHC is of concern, particularly if the ER status of a tumor is based on DCC results alone.

CLINICAL RELEVANCE: Because most canine mammary tumors are fixed in formalin prior to histologic evaluation, an IHC assay that identifies ER-positive cells is desirable. Adjunctive antiestrogen therapy could be administered to dogs with ER-positive tumors.

Alternate JournalAm. J. Vet. Res.