Objectives: To study the immunohistochemical expression of CD10 in stromal cells of breast carcinoma and to correlate the expression of CD10 with various clinicopathological prognostic factors such as the size of the tumor, histological grade, lymph node status, and estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2/neu protooncogene (HER2-neu) status. This evidence concerns the gene ESR1 and breast carcinoma.