Abstract: It has now been determined that cancer cells have a specific surface protein existing as a glycoprotein which functions to stimulate specific cell-mediated immune response in the host directed toward the specific cancer. The following disclosure includes the method of identification of the specific cell surface protein and procedures utilizing the protein, or preferably the active peptide in testing for specific cancers and immunization. Having identified the specific cell surface protein for a cancer, the n-terminal tridecapeptide or the active portion of the peptide may be synthesized and utilized in testing and immunization. Further, the specific cell surface protein and active peptide for ductal carcinoma (brest cancer) is identified herein.