Prognostic significance of mitotic figures in metastatic mammary ductal carcinoma to the lymph nodes

We previously reported that the number of mitotic figures in metastatic mammary carcinoma to the lymph nodes accurately predicted the outcome of patients with invasive ductal carcinoma with nodal metastasis. To confirm these previous findings, the present study investigated the number of mitotic figures and other histologic characteristics in metastatic mammary carcinoma to the lymph nodes and their associations with patient outcome according to nodal status and the histologic grade of primary invasive ductal carcinomas in a different series of 1039 patients with invasive ductal carcinoma. Multivariate analyses examining well-known clinicopathologic factors, the number of mitotic figures in the primary invasive ductal carcinomas, the grading system for lymph vessel tumor emboli, the p53 Allred score risk classes of tumor-stromal fibroblasts forming and not forming a fibrotic focus, and 9 histologic features of metastatic mammary carcinoma to the lymph nodes were performed. The presence of 6 or more mitotic figures in metastatic mammary carcinoma to the lymph nodes significantly increased the hazard ratios for tumor recurrence and tumor-related death among patients with invasive ductal carcinoma as a whole, those with nodal metastasis, and those with a histologic grade of 2 or 3. The presence of 6 or more mitotic figures in metastatic mammary carcinoma to the lymph nodes also significantly increased the hazard ratio for tumor recurrence among patients with histologic grade 1 invasive ductal carcinoma. In conclusion, this study clearly confirmed the excellent outcome predictive power of the number of mitotic figures in metastatic mammary carcinoma to the lymph nodes.