During the past 100 years, there have been two major controversies with regard to the treatment of primary breast cancer. The first controversy, which occurred approximately 35 years ago, questioned the performance of radical mastectomy, as originally proposed by Halsted in the 1890s. That controversy was resolved by the use of laboratory and clinical research, hypothesis formulation, and evaluation of the efficacy of the latter through the conduct of randomized clinical trials. A second major controversy arose when magnetic resonance imaging began to detect the presence of tumor multicentricity in many breast cancer patients, resulting in a resurgence in mastectomy in women who could have been treated with breast-preserving surgery. Because the use of science resolved the first controversy, I investigated whether there was scientific evidence to justify the current reversion to mastectomy. Extensive examination of the vast amount of recent medical literature related to that subject, that is, individual articles, review articles, and reports from the use of clinical trials, demonstrated that many physicians are not familiar with the scientific method, and thus, were unable to present, in those articles, credible evidence to support mastectomy in the presence of tumor cell multicentricity. Aside from the randomized clinical trial conducted by the National Surgical Adjuvant Breast and Bowel Project begun in 1976, which demonstrated no statistically significant difference in disease-free survival, distant disease-free survival, and overall survival between mastectomy and lumpectomy with or without radiation therapy, there has been no information in any of the few recently conducted studies involving multicentricity to justify the current resurgence in mastectomy.