Selective biopsy of the opposite breast.

The bilaterality of breast cancer detected by performing a contralateral biopsy has been reported to be 14%. Since the majority of cancers detected were noninfiltrating, a mastectomy was not always performed because of either the advanced stage of the presenting carcinoma or the age of the patient. This study was undertaken to determine the yield of contralateral cancers in younger patients with a better prognosis. Patients younger than 65 years with clinical Stage I and II initial breast cancers were selected for biopsy of the opposite breast between September 1978 and December 1984. Of 651 consecutive patients treated for breast cancer, 610 had an initial breast cancer and 258 (42%) met the criteria. Forty-three contralateral primary breast cancers were detected, for an incidence of 16.7%. In 11 of these 43 patients there was suspicion that a malignancy might be present; these were all infiltrating carcinomas. In 32 patients a truly random biopsy was performed, and the yield was 14.2%. Four (12.5%) of these were infiltrating cancers, and 28 (87.5%) were in situ carcinomas. By selecting patients for biopsy of the opposite breast, a 16.7% incidence of cancers can be detected. Since these patients were younger than 65 years and have a good prognosis in terms of their initial breast cancer, biopsy of the opposite breast is a worthwhile procedure and should be performed with the hope of improving these patients' ultimate outcome.