NOT LONG ago, a one-stage procedure was standard for diagnosing and treating breast cancer. While such a course of action has decreased in popularity, it is still frequently employed. With that strategy, excisional biopsy, frozen section diagnosis, and mastectomy, if the tissue is malignant, are sequentially performed with general anesthesia. Since the approach best fulfills the Halstedian priniciples governing cancer surgery, it cannot be criticized if the surgeon continues to adhere to those precepts. When the one-stage procedure is used, it is not so critical that the biopsy completely remove all of the tumor since mastectomy immediately follows a positive biopsy finding. Under those circumstances, the role of the pathologist is to determine the diagnosis and not to decide whether the margins of the biopsy specimen are tumor free. When there is a high index of suspicion that the lesion is cancer, the biopsy is usually planned with little or