Diagnosis of metachronous contralateral breast cancer.

The purpose of this study was to compare the characteristics of primary breast cancers (PBCs) and metachronous contralateral breast cancers (MCBCs). Between 1984 and 1996, 236 women treated with curative intent for PBC who developed a MCBC >6 months after initial diagnosis (without previous evidence of distant metastases) were retrospectively evaluated for clinical and pathologic characteristics and method of diagnosis of their tumors. There were more noninvasive cancers among the MCBCs than the PBCs (11.4% and 5.1%, respectively, p < 0.02). Among the invasive cancers, the mean size of the MCBCs was smaller than the PBCs (1.94 versus 2.55 cm, p < 0.001). MCBCs were more likely than PBCs to be mammographically detected (46.2% versus 19.9%, p < 0.001). Tumor size was correlated with the method of diagnosis. The mean tumor size was 1.39, 2.02, and 2.69 cm for mammogram-, physician-, and patient-detected tumors, respectively. Among patients having axillary lymph node dissections, mammogram- and physician-detected tumors were less likely to have lymph node metastases than patient-detected tumors (22.0% versus 41.2%, p < 0.005). Regular follow-up of breast cancer patients diagnoses MCBCs when they are smaller and less likely to have nodal metastases than PBCs mainly because of early mammographic detection.