Abstract
In recent years, it has been pointed out that the efficiency of mass screening by palpation alone is inadequate. During a period of 12 years, between 1986 and 1997, we conducted breast cancer mass screening by a combination of physical examination and real-time whole-breast ultrasonography. A total of 50.378 women aged 30 years or older were examined ; the total number of detected breast cancer cases was 61 and the rate of breast cancer discovery was 0.121%. Of these 61 breast cancer cases 16 were TO (impalpable) breast cancers, which were not detected by palpation by the initial examiner nor by a second examiner. Three of the 16 TO cases were detected due to bloody nipple discharge and the other 13 cases were detected only by ultrasonographic detection of a low-echoic tumor of 10 mm diameter or smaller. Moreover, of these 16 TO case 3 (18.7%) were noninvasive carcinomas and the other 13 (81.3%) were invasive carcinomas. Therefore, we suggest that mass screening using ultrasonography can detect more breast cancers, and a higher proportion of invasive breast cancers, than mass screening using mammography.
The 13 TO cases that we detected based only on the ultrasound findings accounted for 21.3% of the total number of breast cancers that we detected and would have been overlooked had the mass screening involved only a physical examination. Similarly, 4 of the 13 TO cases (30.8%) were diagnosed as being within the normal limits used for mass screening by mammography and would have been over-looked even by mammography + physical examination screening. Although there were no cases with lymph node metastasis, 8 of the breast cancer cases (23.1%) showed invasion into the lymphatic system (ly1-ly2) and 4 (30.8%) showed invasion into the neighboring adipose tissue. Furthermore, the 11 cases (84.6% of the TO cases) that were detected based on the ultrasound findings alone were detected at repeated examinations and were detected, on average, at 3.5 times that seen for annual mass screening by palpation and ultrasonography. We conclude that to conduct significantly beneficial mass screening for breast cancer we must undertake annual mass screening programs using real-time whole-breast ultrasonography, for previous participants and also for firsttime participants.
