Mammographic and ultrasonographic findings in bilateral breast cancer: a comparative study

To compare the results of mammographic and US examinations in unilateral and bilateral breast cancers in routine clinical work, the files of all patients with 825 preoperative mammograms and 525 preoperative US examinations operated on for primary breast cancer in the Oulu University Hospital from 1983 through 1993 were retrospectively reviewed. The only statistically significant difference noted in the mammographic findings was the false-negative rates in unilateral, bilateral and metachronous second breast cancers (6.8, 16.3 and 23.3 %, respectively). The differences were mainly due to the lower sensitivity of mammography in the detection of palpable bilateral breast cancers. The false-negative rate of US was also significantly higher in bilateral breast cancers (23 %) than in unilateral cancers (11 %), and significantly higher for nonpalpable than palpable cancers in both the bilateral and the unilateral groups. The mammographic failure rates and the difference between these two groups were most pronounced during the early study period, which underscores the importance of experience and dedicated imaging technique. The smaller tumour size at the time of diagnosis and probably the loss of the opposite breast for comparison have contributed to the higher false-negative rates in bilateral breast cancer.