Two trials of mass screening for breast cancer using mammography were carried out in Tokushima prefecture. A total of 9 cases (0.24%) among 3, 707, and 14 cases (0.56%) among of2, 500 were diagnosed as breast cancer. In over half of the mammographic examinations, breast cancer was detected as a mass shadow. We consider that one of the quality control parameters for mass screening using mammography is imaging of mass shadow.
