Abstract： AIM:To study the expression of CD44~+/CD24~-phenotype and its association with the molecular subtypes of breast cancer in breast cancer. METHODS:Using immunostaining ER, PR, HER2, CK5/6 and P53 to classify the material into 5 molecular subgroups:basal-like subgroup, Luminal A subgroup, Luminal B subgroup, Her2 over-expressing subgroup and Normal breast-like subgroup. Double-staining immunohistochemistry (IHC)was applied for the detection of CD44~ +/CD24 ~-cells. The correlations of the expression of the CD44 ~+/CD24~-to molecular subtypes of breast cancer were analyzed. RESULTS:In 217 cases of breast cancer, basal-like subgroup:29 cases, Luminal A subgroup:130 cases, Luminal B subgroup:15 eases, Her2 overexpressing subgroup:21 cases, Normal breast-like subgroup:22 eases. The expression rates of CD44 ~+/CD24~-in total breast cancer, basal-like subgroup, Luminal A subgroup, Luminal B subgroup, Her2 over-expressing subgroup, Normal breast-like subgroup were 38%, 69%, 36.2%, 26.7%, 19%, 31.8%. The expression rates of CD44 ~+/CD24~-phenotype was high in basal-like breast cancer, which was significantly different from the other subgroups (P = 0. 003). CONCLUSION:The study suggests that the CD44 ~+/CD24~-breast cancer stem cells in tumor tissue is associated with basal-like cancer, and other breast cancer stem cell markers remain to be identified.