Breast cancer mortality in Japan is at an alltime high despite increased early detection and better methods of treatment. It is important, of course, that optimal treatments should be chosen for individual patients in order to decrease the risk of death. Appropriately applied therapies can result in a good outcome when the histologic information about each individual breast cancer patient, including histological grading of the malignancy, is well clarified. At the St. Gallen International Consensus Conference 2005, the definition of risk categories for patients with operable breast cancer was based on several pathological findings, such as regional nodal status, histologic and/or nuclear grade, HER2/neu overexpression/amplification, and presence of peritumoral vascular invasion1). With regard to ascribing a risk category for patients with operable breast cancer, histologic and/or nuclear grading plays an important role in dividing low risk cases from intermediate risk cases in node-negative patients. Node-negative patients rated Grade 1 (low grade) are classified as a low risk group, and those rated Grade 2 (moderate grade) or Grade 3 (high grade), are classified as intermediate risk groups. When we decide to provide appropriate adjuvant therapy to node-negative breast cancer patients according to the Consensus, we should divide patients at low risk from those at intermediate and other risk levels.

The histological grading of malignancy is the most classical evaluation method for prognosis in breast cancer patients 2-5) and it is the simplest method, requiring only hematoxylin-eosin staining. Although judging the histologic grade of the malignancy is the most common and the most important process for arriving at a prognosis in