It is a branch of immunology that deals with the interaction of system with the tumor cells. Tumor immunology may be a growing field of research which aims to get new and innovative tumor or cancer immunotherapies which will be wont to retard or treat the progression of tumor. The immune reaction , which incorporates the popularity of tumor-specific antigens, is vital because it will help within the development of targeted therapy and tumor marker-based diagnostic tests. The system can answer tumor cells in two ways: by reacting against tumor-specific antigens (molecules that are unique to cancer cells) or by reacting against tumor-associated antigens (molecules that are expressed differently by cancer cells and normal cells). Tumors that are caused by viruses display viral antigens which function tumor antigens. The expression of molecules of cell surface produce to tumor antigens on the surface of the tumor cell. Monoclonal antibodies which react specifically with tumor cells are wont to characterize putative human tumor antigens. Some tumor antigens contains those molecules which are unique to the tumor cell but not almost like the traditional cell. Some tumor antigens are sometimes qualitatively same as those found on normal cells but are over expressed on the tumor cell.