Would you recommend tamoxifen x 5 years following mastectomy in a male with pure DCIS?  

I would not. The risk of developing contralateral breast cancer in a woman with DCIS is about 5% per decade, or 0.5% per year. At this level of risk, chemopreventive tamoxifen is an appropriate consideration. The risk of contralateral breast cancer in a man with DCIS is uncertain, but is almost cert...