Carcinoma of the male breast (MBC) is an uncommon phenomenon, accounting for <1% of all malignancies in man. It represents a biologically heterogeneous disorder, and its clinical course may vary from indolent and slowly progressive to rapidly metastatic disease. Most of our current knowledge regarding its biology, natural history, and treatment strategies has been extrapolated from its female counterpart. Information regarding prognostic relevance of new molecular markers is limited. At the European Institute of Oncology we performed a study showing data in which p21Waf1 and p27Kip1 proteins were evaluated in a series of male breast cancer patients. Our data suggest that the immunohistochemical evaluation of p21Waf1 and p27Kip1 expression in male breast carcinomas may be a further useful marker for selecting patients who express functional proteins that can be predictive for the most efficient endocrine response. Moreover, searching for more conservative treatment, we introduced in our clinical practice sentinel node biopsy, and if present, sentinel node biopsy of the internal mammary chain. The potential clinical implications of complete nodal staging are far-reaching, and give us a major new opportunity to stratify male patients with breast cancer for appropriate surgery as well as giving valuable prognostic information. Male breast cancer has biological differences compared with female breast cancer. It responds to hormonal manipulation and chemotherapy, but optimal treatment regimens in males are unknown. By analogy to the female breast cancer, post-mastectomy radiotherapy should be proposed in case of advanced T stage and/or lymph node positivity (considering the small volume of the male mammary gland, we suggest post-mastectomy irradiation in case of T >1 cm and/or presence of >1 metastatic axillary lymph node). Breast conserving surgery, performed in selected cases of male breast cancer, should be always followed by radiotherapy. Despite a wealth of small retrospective studies on MBC, its rarity means there is a lack of prospective randomized controlled treatment trials, which needs to be addressed if significant advances are to be made in the treatment of this unusual challenging disease.