Bilateral breast cancer: the frequency of undiagnosed cancers.

The risk of developing cancer in the contralateral breast is five to seven times the risk of cancer occurrence for the normal female population. In patients in 365 consecutive operations, 15 frankly invasive cancers and four metastatic lesions were found in the contralateral breast as well as an additional 28 lesions in situ, totaling 13%. An additional 30% of the patients had severe dysplasia with an unknown potential for becoming cancerous. Only less than one third of the cancers in the contralateral breast were symptomatic (by palpation or mammography or both) but not recognized at the time of primary treatment. The majority of lesions in the contralateral breast are due to a second primary growth, and only a minority is metastatic. The results of 203 bilateral operations consisting of a modified subcutaneous mastectomy with axillary lymph node dissection and radiation are presented; this cosmetically acceptable procedure reduces the number of cancers in the contralateral breast to an incidence of 1% to 2%.