Based on H and E staining for identification of tumor cells, immunofluorescence was used to quantify the frequency of CD44-/CD24-, CD44+/CD24-, CD44-/CD24+, and CD44+/CD24+ tumor cells in 576 breast cancer tissue specimens, including a training group (n = 355) and testing group (n = 221) using anti-CD44 and anti-CD24 antibodies. This evidence concerns the gene CD44 and breast cancer.