Several interesting aspects of breast cancer were covered at this year's American Society of Clinical Oncology meeting. Sentinel lymph node (SN) mapping is now in widespread use, in concert with the general trend toward trying to decrease the morbidity of breast cancer surgery. With every advance, however, comes new challenges, and there was a timely presentation from Giuliano's group addressing the controversial issue of how to interpret the presence of cells in the SN seen only with keratin stains but not by routine hematoxylin and eosin stains. Two abstracts addressed the issue of whether for certain women with invasive breast cancer radiation therapy could be omitted after lumpectomy. Another interesting topic related to hormonal issues in the adjuvant treatment of premenopausal women. An analysis from the ZIPP-TRIAL reported on bone marrow density studies in young women given two years of ovarian suppression in the adjuvant setting: it seems that the loss of bone density may be reversible and, more interestingly, may be prevented with concurrent tamoxifen. Two other presentations looked at the prognostic significance of drug-induced amenorrhea in young women treated with adjuvant chemotherapy and at the efficacy of ovarian suppression during chemotherapy in preserving fertility. In an unpublicized presentation, Mary-Claire King presented very interesting results from the National Surgical Adjuvant Breast and Bowel Project Breast Cancer Prevention Trial suggesting that tamoxifen may be an effective chemopreventive drug for women with BRCA2, but not BRCA1, mutations. Two important presentations re-analyzed the outcome of the pivotal trials using Herceptin to treat metastatic breast cancer and nicely show that FISH analysis of HER-2 overexpression is a more accurate indicator of response to Herceptin than immunohistochemical staining. Finally, there were two interesting presentations related to tamoxifen resistance which may be relevant clinically, pertaining to subsequent raloxifene use and the interaction of the estrogen receptor and EGF receptor pathways, respectively.