Immunohistochemical staining with anti-CacyBP/SIP antibodies of sections prepared from mammary tumors taken 8 weeks after DMBA treatment was similar to the immunostaining of sections prepared from the pathologically changed mammary tissue taken 6 weeks after DMBA treatment, but the CacyBP/SIP immunoreactivity was much more intensive. Here, CACYBP is linked to breast cancer.