Establishment of histological criteria for high-risk node-negative breast carcinoma for a multi-institutional randomized clinical trial of adjuvant therapy

Background: A multi-institutional randomized clinical trial of adjuvant therapy for patients with high-risk node-negative (n0) breast cancer has been undertaken in Japan. The pathology panel was organized in order to establish histological criteria to identify patient groups with higher rates of recurrence. Methods: Initially, three pathologists independently judged the nuclear grade, composed of nuclear atypia and mitotic counts, of 100 n0 invasive ductal carcinomas, focusing on interobserver variation of the nuclear grade and its correlation with patient prognosis. These pathologists then gave consensus histological types and nuclear grades for 130 other n0 breast carcinomas and examined the prognostic significance of the grade. Results: In the first study, nuclear grade 2-3 significantly identified a patient group with a rate of recurrence of 17-20% by any pathologists and the degree of agreement for the grade was fair. In the second study the consensus type and nuclear grade identified a group (n = 66) with a 22% recurrence rate and another group (n = 64) with a 3.6% recurrence rate at 10 years. In 12 tumors, the resection-fixation interval of the tumor did not generate any significant difference in mitotic counts. Conclusions: The histological type and the nuclear grade clearly identified a higher-risk patient group with n0 breast carcinoma, and may be applied to the multi-institutional protocol study when the criteria have been well standardized by the pathologists.