In the prognosis of breast cancer, pathologists are facing a time of consolidation. Widely accepted guidelines have been gained only recently, with expectations that further developments are soon to come. Prognostic data influence systemic treatment decisions that are largely dependent on stage criteria of lymph nodes and tumor size as well as menopausal status. Some researchers propose that lymph node removal has no therapeutic consequences and may not be necessary if the majority of women are to be treated by chemotherapy. Some pathologists take this information as gospel for simplifying the management of a complex disease, whereas others take information available at different levels of certainty and set treatment threshold probabilities on an individual patient basis. With regard to invasive carcinoma and systemic therapy, I believe that combined histologic grade, including an emphasis on mitotic counts and other proliferation indicators, provides information at either end of the staging spectrum. Thus, high-grade, small tumors are likely to recur and low-grade, large tumors are unlikely to recur, at least within a 2- to 5-year period. Whether use of this information can be extended and verified for use in therapeutic decision making for neoadjuvant chemotherapy or various escalated chemotherapy regimens remains to be established. However, this use of prognostic indicators or predictors to indicate therapeutic responsiveness represents the field's immediate future. There are separate and important indicators of local treatment failure in the breast following conservation. It is likely that the extensiveness of DCIS is the major determinant of local recurrence and that its interaction with extensiveness, type of carcinoma in situ, and the branching ductal anatomy of the breast are of primary importance. Finally, the groups of conditions recognized as DCIS continue to provide a fertile field of questioning and discovery. Unassailable at the present time is the evidence that small, low-grade lesions may be treated effectively by planned wide local excision. Precise guidelines and further information are necessary from planned trials stratified by size and histologic criteria. Prognostic considerations have only become important in guiding treatment decisions in the past few decades. The escalating importance of prognostic categories derives from the availability of more varied treatment options, which have applications in the different clinical settings discussed in this chapter.