Usefulness of ultrasonography combined with conventional physical examination in mass screening for breast cancer: a retrospective study of Yamanashi Health Care Center results from 1989 to 1994.

We retrospectively analyzed the records for 34,474 women who participated in mass screening for breast cancer by physical examination with or without ultrasonography (US) at Yamanashi Health Care Center between April, 1989 and March, 1994 to evaluate the usefulness of US in mass screening. In one group (15,935 women) conventional physical examination with inspection and palpation alone had been performed, and in another (18,539 women) both conventional physical and US examinations were performed. Breast cancer was detected in 27 of the women (0.08% of the total group screened), 22 of whom were in the group examined by US; moreover, 16 of these 22 women had early breast cancer, which was a non-palpable tumor in 13. Half of the 22 women were examinees under the age of 50 years. Of the 22 tumors detected in the groups examined by US, 16 (73%) were early breast cancer. The overall detection of early breast cancer (0.09%) in the US group was significantly higher than that (0.01%) in the group examined by conventional methods (P < 0.05). Of the tumors detected in the US group, 59.1% were non-palpable. These results suggest that early and non-palpable breast cancer can be detected using US, and the incidence of detection of such tumors in women under the age 50 years is increased in mass screening including US examination. This examination is effective in mass screening for breast cancer, especially for early and non-palpable breast cancer tumors.