CD24, also known as the heat-stable antigen （HSA） or small-cell lung carcinoma cluster 4 antigen, is a highly glycosylated protein anchored to the cell membrane via glycosylphosphatidylinositol （GPI）. It is a small mucin-like molecule expressed in various cell types, including B cells, immune cells, and tumor cells. CD24 acts as a "don't eat me" signal by interacting with Siglec-10 on macrophages, inhibiting phagocytosis and promoting immune evasion in cancer. This protein is overexpressed in many solid tumors, such as breast, lung, and colorectal cancers, and is associated with tumor progression and poor prognosis. Unlike CD47, CD24 is not expressed on red blood cells, making it a promising target for cancer immunotherapy without the risk of blood toxicity. Current research focuses on developing CD24-targeted therapies, including monoclonal antibodies and nanoparticle-based delivery systems, to enhance anti-tumor immunity.