Using indirect immunofluorescence (IIF), an anti-centromere protein CenpG-serum was verified. Western blot of the protein extracts of 31 samples of breast cancer tissues and their normal (not cancerous ) tissues a little far away from them in the same individuals showed that, in the majority of the tests (71%), centromere protein CenpG over expressed in breast cancer tissues. And moreover, a kind of protein component whose molecular weight is 43 kd, and which can be recognized by anti-CenpG serum was found in two of the cancer samples. The results suggested that CenpG (together whith it, there may be other relative components),which has been found and named recently, may be related to cancer,and its differential expressing is probably related to malignant cell proliferation.