A monoclonal antibody is a special type of antibody that is produced in cells grown in a laboratory. Monoclonal antibodies are so specific in their action that they bind only to certain portions (termed antigenic determinants) of specific molecules, called antigens.
Some monoclonal antibodies are used in laboratory tests for the diagnosis of cancer.
Other monoclonal antibodies are biological therapeutics used in the treatment of certain types of cancer. For example, Herceptin (generic name, trastuzumab) is a monoclonal antibody that is used to treat certain types of breast cancer.