CD24 is a mucin-like adhesion molecule that has recently raised attention and lent substantial improvements for our understanding of tumor biology. Functionally, CD24 enhances the metastatic potential of malignant-cells, because it has been identified as a ligand of P-selectin, an adhesion receptor on activated endothelial cells and platelets. Moreover, it has been described as a diagnostic molecular marker of malignant tumor and for patient prognosis. This article reviews the experimental and clinical data on CD24 expression and carcinomas from the point of view of tumor biology. Based on the research, CD24 expression will be analyzed as a potentially significant parameter for a wide variety of human cancer diagnoses. Understanding the functions and implications CD24 might aid the clinician in the selection of an appropriate therapy for individual patients: for example, the intravenous administration of C1324-specific antibodies to treat cancers.