Trial of early detection for breast cancer by itinerant mass screening.

Since 1977 mass screening for breast cancer has been conducted in Miyagi Prefecture, Japan. The main activities involve itinerant screening in the communities and group screening at the workplaces. In addition to the above two screenings, examinations were also carried out at a Detection Center. The total number of examinees was 94,593. Breast cancer was detected in 116 subjects (0.12%) during mass screening. In contrast, the rate was 3.1% at the Center examination. Early cancer was more frequently detected during mass screening. The cytologic studies of nipple discharge was performed in 14,314 subjects (15.3%). Positive findings were seen in five (0.005%). In the high risk group, the detection rate (0.35%) was higher than that (0.12%) among general examinees. The higher detection rate in the high risk group may have been due to both the high frequency of breast cancer and the detection of nonpalpable breast cancer by mammography.