Risk of subsequent contralateral breast carcinoma in a population of patients with in-situ breast carcinoma.

One hundred ninety-one cases of unilateral noninvasive breast carcinoma were studied with regard to the development of subsequent cancers in the contralateral breast. The majority of patients were treated by mastectomy and have been followed for an average of nine years. Their overall survival did not differ significantly from that of age-specific population survival figures for U. S. women. Among all cases, 13 or 6.8% subsequently developed contralateral carcinoma; 3.1% of these contralateral tumors were invasive. The authors found only one histological type, namely lobular carcinoma in-situ for which the development of subsequent contralateral carcinomas was statistically significant. Seven of the 68 women with this type developed second breast cancers (10.3%; 4.4% of these were invasive). These data suggest that the occurrence of clinically apparent subsequent cancers developing in the opposite breast following the diagnosis of in-situ carcinoma is relatively small.