This review emphasizes tissue pathology and its practical relevance to patient management in premalignant breast disease and established breast cancer. The rationale and criteria for recognizing benign lesions that indicate a subsequent increased risk for cancer development are now well established, having been confirmed in several large epidemiologic studies. Our understanding of the heterogeneous nature of ductal carcinoma in situ (DCIS) continues to evolve. Recent efforts to classify DCIS into clinically meaningful categories underscore the central role of histopathology in the management of this disease. Through long term follow up studies, small examples of noncomedo DCIS treated by biopsy alone may predict local recurrence. Adequate surgical excision, however, avoids this possibility in the predominance of such cases. For invasive carcinomas, prognostic issues extend beyond predicting survival after local treatment. Now that the efficacy of systemic chemotherapy is established, the question is whether this therapy will be of use to a particular patient or group of similar patients. The list of possible clinically useful subcategories of prediction is growing and under active development. Prognostic factors that are in general use, having been repeatedly validated, particularly stage and histologic grade, as well as those that are emerging but in need of validation, are reviewed.