Abstract: Accurate diagnosis is a necessary step in the management of breast cancer. In women with breast cancer, diagnosis can confirm the presence of the disease, reduce treatment delays, and clarify the predictive and prognostic features of the cancer, which help in planning treatment and counseling women. In women with benign breast conditions, accurate diagnosis avoids erroneous treatment for breast cancer, which can have devastating consequences for the woman and unnecessarily consumes resources. The panel distinguishes between a “clinical diagnosis” of breast cancer (one based on signs and symptoms and imaging findings) and a “pathologic diagnosis” of breast cancer (one based on microscopic examination of cellular or tissue samples). The panel agrees that all women should have a pathologic diagnosis of breast cancer before they are given definitive treatment for the disease, no matter how strongly their clinical findings suggest cancer. The tools for clinical diagnosis include history, clinical breast examination, ultrasound, and diagnostic mammography; these tools provide valuable information and play important supplemental roles in ascertaining the presence of breast cancer. Mammography and ultrasound also help determine the extent of disease within the breast, which is essential when breast-conserving therapy can be offered to women. The tools for pathologic diagnosis include fine-needle aspiration biopsy, core needle biopsy, and standard surgical biopsy. The panel noted that each of these tools has potential benefits and limitations in the limited-resource setting, and concluded that the choice among them must be based on the available tools and expertise. The triple test—checking for correlation of pathology findings, imaging findings, and clinical findings—was identified as a critical practice in diagnosing breast cancer. Panelists uniformly agreed that mastectomy should not be used to diagnose breast cancer, noting that accurate diagnosis can be made by less invasive means. Expertise in pathology was identified as a key requirement for ensuring reliable diagnostic findings. Several approaches were proposed for improving breast pathology, including training pathologists, establishing pathology services in centralized facilities, and organizing international pathology services.