Immunohistochemical detection of P⁵³ in canine mammary tumors

Mammary gland tumors are the most common neoplasms in female dogs and represent the second most frequently recognized tumors in dogs. Incidence of mammary tumor is as high as 50 per cent of all neoplasms in female dogs as compared to breast cancer in women. The prevalence of Estrogen Receptor (ER) Progesterone Receptor (PR) has been reported to be < 50% in mammary tumors in dogs and 60–75% in breast cancer in human beings. Apart from hormonal receptors, proliferative markers like P⁵³ and C-erb B2 can be measured by using IHC studies which are of prognostic relevance. In the present study IHC studies were carried out on 24 malignant CMTs consisting of adenocarcinoma (20), solid carcinoma (2), mixed mammary tumor (2) to know the rate of proliferation. P⁵³ mutation was evident in 5 (20.83%) of 24 CMTs. P⁵³ mutation was evident in 27.2% of the tumors that were declared positive for either or one of the hormone receptors. 20% of adenocarcinomas (4) and 50% of solid carcinoma (1) were found positive for P⁵³ immunoreactivity. None of the mixed mammary tumors could express the P⁵³ positivity.