Objective: Patients who have had cancer in one breast are at high risk for cancer in the contralateral breast. These bilateral cancers may be synchronous or metachronous. If the manifestations on mammography were similar in both breasts, an aggressive search for the mammographic findings of the first breast cancer might lead to early detection of the contralateral cancer. The purpose of this study was to evaluate mammograms for patients with bilateral cancers to determine whether the mammographic appearance of the contralateral cancer is likely to be the same as that of the first cancer.
Materials and methods: We retrospectively reviewed the pathologic and mammographic records of 69 patients with surgically proven bilateral primary breast cancer. Thirty four of 69 (49%) had synchronous cancer, and 35 (51%) had metachronous cancer. Mammographic appearances were classified as microcalcifications, spiculated mass, nonspiculated mass (whether circumscribed or poorly defined), asymmetric or developing density, architectural distortion, and normal. Multiple findings were subclassified as major and minor findings. All findings were compared between both breast cancers, and statistical significance was determined by the two-sample Z test.
Results: Forty six (67%) of 69 patients had different major mammographic findings in the contralateral cancer. Of 30 patients whose first cancers had microcalcifications, 20 (67%) had microcalcifications in the contralateral cancer. Of 39 patients whose first cancers lacked microcalcifications, 17 (44%) had microcalcifications in the contralateral cancer. This difference was statistically significant (p = .02). Of 26 patients whose first cancers had spiculated masses, 9 (35%) had a contralateral spiculated mass. Of 43 patients whose first cancers lacked spiculated masses, 12 (28%) had a contralateral spiculated mass. This difference was not statistically significant (p = .22).
Conclusion: Our results show that contralateral tumors usually have major mammographic findings different from those of the first cancer, and the mammographic signs of the first cancer do not indicate the most likely appearance of cancer in the contralateral breast. Evaluation of a contralateral mammogram should be performed without regard for the mammographic findings for the first cancer.