Prevalence of CD44+/CD24-/low cells in breast cancer may not be associated with clinical outcome but may favor distant metastasis.

PURPOSE Breast cancer is composed of phenotypically diverse populations of cancer cells. The ability to form breast tumors has been shown by in vitro/in vivo studies to be restricted to epithelial tumor cells with CD44(+)/CD24(-/low) characteristics. Validation of these findings with respect to detection in clinical samples, prognosis, and clinical relevance is in demand. EXPERIMENTAL DESIGN We investigated breast cancer tissues for the prevalence of CD44(+)/CD24(-/low) tumor cells and their prognostic value. The study included paraffin-embedded tissues of 136 patients with and without recurrences. In addition, a breast cancer progression array with normal, carcinoma in situ, and carcinoma tissues was analyzed. We applied double-staining immunohistochemistry for the detection of CD44(+)/CD24(-/low) cells. Evaluation was by microscopic pathologic inspection and automated image analysis. RESULTS CD44(+)/CD24(-/low) cells ranged from 0% to 40% in normal breast and from 0% to 80% in breast tumor tissues. The prevalence of CD44(+)/CD24(-/low) tumor cells in 122 tumors was < or =10% in the majority (78%) of cases and >10% in the remainder. There was no significant correlation between CD44(+)/CD24(-/low) tumor cell prevalence and tumor progression. Although recurrences of tumors with high percentages of CD44(+)/CD24(-/low) tumor cells were mainly distant, preferably osseous metastasis, there was no correlation with the event-free and overall survival. There was no influence on the response to different treatment modalities. CONCLUSIONS Our findings suggest that the prevalence of CD44(+)/CD24(-/low) tumor cells in breast cancer may not be associated with clinical outcome and survival but may favor distant metastasis.