In the present article we have determined the expression of CD44 and CD24 in human breast tumors using double-staining immunohistochemistry and have correlated the presence of CD44+/CD24- cells to subgroups of breast cancer, classified using the expression of ER, PgR, HER2, CK5/14 and EGFR, as well as by mRNA expression profiles. The gene discussed is CD44; the disease is breast carcinoma.