Tumor antigens are specific molecules found on the surface of cancer cells that can trigger an immune response. These antigens can be proteins, carbohydrates, or other types of molecules that are either unique to tumor cells or present in higher amounts compared to normal cells. They help the immune system recognize and attack cancer cells. There are two main types of tumor antigens: tumor-specific antigens (TSAs), which are unique to cancer cells, and tumor-associated antigens (TAAs), which are found in both normal and cancerous cells but at different levels. Understanding these antigens is crucial for developing targeted cancer therapies and vaccines.