Expression of ALDH1 in axillary lymph node metastases is a prognostic factor of poor clinical outcome in breast cancer patients with 1-3 lymph node metastases

Recently, evidence in support of the cancer stem cell (CSC) hypothesis has been accumulating. On the other hand, it has been reported that the expression of aldehyde dehydrogenase 1 (ALDH1) in primary breast cancer is a powerful predictor of a poor clinical outcome, and that breast cancer stem cells express ALDH1. According to the CSC hypothesis, development of metastases requires the dissemination of CSC that may remain dormant and be reactivated to cause tumor recurrence. In this study, we investigated whether the detection of CSC in axillary lymph node metastases (ALNM) might be a significant prognostic factor in patients with breast cancer. From 1998 to 2006, 40 primary breast cancer patients with ALNM, the number of metastatic nodes varying in number from 1 to 3, underwent surgery at Okayama University; of these, 15 patients developed tumor recurrence. We retrospectively evaluated the common clinicopathological features and the expression of ER, HER2, ALDH1, and Ki67 in both the primary lesions and the ALNM, and analyzed the correlations between the expression of these biological markers and the disease-free survival (DFS). Expression of ALDH1 in the ALNM was significantly associated with the DFS (P = 0.037). Evaluation of biomarker expression in ALNM could be useful for prognosis in breast cancer patients with 1-3 metastatic lymph nodes.