Increased lymph node positivity in multifocal and multicentric breast cancer.

BACKGROUND: Multifocal and multicentric (MF/MC) breast cancers have been reported to be associated with increased lymph node metastases. The limited data on this issue prompted us to investigate the pathologic and clinical differences between unifocal and MF/MC breast cancer. STUDY DESIGN: Between 1990 and 2002, 1,322 patients with operable invasive breast cancer underwent a definitive operation at our Breast Clinic. Patients with MF/MC breast cancer (n=147, 11%) were compared with patients with unifocal breast cancer (n=1,175; 89%) in terms of pathologic and clinical characteristics. RESULTS: Patients with MF/MC were found to have a higher frequency of lymph node metastases when the largest diameter was used as a tumor size estimate for MF/MC cancer (unifocal T1 and T2, 35% and 49%, respectively, versus MF/MC T1 and T2, 48% and 67%, respectively; p=0.05 and p=0.003, respectively). When the combined diameter assessment was used, the frequency of lymph node positivity was similarly higher in MF/MC patients versus unifocal patients (unifocal T1 and T2, 35% and 49%, respectively, versus MF/MC T1 and T2, 49% and 61%, respectively; p=0.08 and p=0.046, respectively). At a median followup of 55 months (range 12 to 153 months), 5-year disease-free survival (DFS; unifocal, 88% versus MF/MC, 82%, p=0.14) and overall survival (OS) rates (unifocal, 92% versus MF/MC, 93%, p=0.43) did not show any significant difference between two groups. CONCLUSIONS: Our data suggest that breast tumors with multiple foci have a different biology, with an increased metastatic potential to axillary lymph nodes, regardless of tumor size, that reflects an advanced stage. The clinical relevance of the currently used TNM classification system, which uses the diameter of the largest nodule, is supported by our findings.