Male and Female Breast Cancer – Differences in DNA Ploidy, p21 and p53 Expression Reinforce the Possibility of Distinct Pathways of Oncogenesis

Abstract

Aim: The purpose of this study was to compare the immunohistochemical profile of cell cycle inhibitors of G1/S phase transition (p21, p53 and pRb), Ki-67 proliferation marker and DNA ploidy in male (MBC) and female breast cancer (FBC). Material and Methods: One hundred patients (50 non-consecutive cases of FBC and an equal number of MBC) were selected according to homogeneous features regarding age, histological type, tumour grading, nodal status and absence of neoadjuvant therapy. The expression of p21, p53, pRb and Ki-67 was assessed by immunohistochemistry, and DNA ploidy was analysed by flow cytometry. Correlations between variables were evaluated using the χ² test. Results: The incidence of DNA aneuploid, p21-positive and p53-negative tumours was significantly higher in MBC than in FBC; pRb and Ki-67 revealed no statistically significant differ- ences between the two entities. In MBC, high tumour grade correlated with aneuploidy, Ki-67 and pRb positivity; ploidy and p53 were also associated. In FBC, only ploidy and grade showed a strong correlation. Conclusion: The significant dissimilarities regarding DNA ploidy, p21 and p53 in these quite homogeneous groups of FBC and MBC point to different genomic instability and to differences in cell cycle proliferative control, reinforcing the view of somewhat distinct tumour oncogenesis.