Cells with distinct phenotypes and stem cell-like properties have been reported to exist in breast cancer. The aim of the present study was to investigate the clinicopathologic and prognostic significance of the CD44(+)/CD24(-/low) and CD44(-)/CD24(+) tumor phenotypes' prevalence. Double immunohistochemistry was applied on a series of 155 paraffin-embedded breast tissue specimens to detect CD44 and CD24. Evaluation of the phenotypes was performed by image analysis. The prevalence of CD44(+)/CD24(-/low) and CD44(-)/CD24(+) tumor cells was 58.7% and 82.6%, respectively. The dominance of the CD44(+)/CD24(-/low) tumor cells was inversely associated with lymph node metastasis (P = .019) and tended to inversely associate with the stage of the disease (P = .068). Moreover, the prevalence of CD44(+)/CD24(-/low) was found to exert no significant impact on patients' prognosis although it displayed a tendency toward an increase in disease-free survival (P = .074). On the other hand, the prevalence of CD44(-)/CD24(+) tumor cells was found to have no clinicopathologic significance. However, it was found to exert an unfavorable impact on both relapse-free (P = .009) and overall survival (P = .046) of the patients with breast carcinomas of intermediate differentiation (grade 2). In breast tissue, CD44(+)/CD24(-/low) tumor cells seem to be associated with lack of lymph node metastasis and a tendency toward an increase of the relapse-free survival of the patients. On the contrary, tumor cells with the phenotype CD44(-)/CD24(+) seem to identify patients with worse disease-free and overall survival within the group of intermediate-grade differentiation patients whose prognosis is difficult to assess.