Axillary lymph node status and prognosis in multifocal and multicentric breast carcinoma

According to tumor-node-metastasis classification, tumor size should be based only on the largest tumor for multifocal and multicentric (MFMC) carcinomas. We estimated tumor size of MFMC carcinoma using either largest dimension of the largest tumor (dominant tumor size) or sum of the largest dimension of all tumors (aggregate tumor size), and compared the risk of axillary lymph node metastasis and prognosis between MFMC and unifocal carcinoma. We retrospectively reviewed the file records of 3,616 patients with MFMC (258 patients, 7.1%) and unifocal (3,358 patients) carcinoma. In T1 and T2 tumor subgroups, using dominant (p = 0.001 and p < 0.001) and aggregate (p = 0.017 and p = 0.004) tumor size axilla-positivity ratio was significantly higher in MFMC carcinoma compared with unifocal carcinoma. In stage I and II disease classified according to either dominant or aggregate tumor size, there was no significant survival difference between MFMC and unifocal carcinoma patients. In patients with stage III disease by dominant and aggregate tumor size disease-free survival was significantly worse in MFMC carcinoma compared with unifocal carcinoma (p = 0.036 and p = 0.041); multifocality and multicentricity had no independent prognostic significance (p = 0.074 and p = 0.079). The risk of axillary metastasis in MFMC carcinoma was higher than unifocal carcinoma, regardless of the method employed for tumor size estimation. MFMC carcinoma staged according to either dominant or aggregate tumor size had similar survival with unifocal carcinoma. We recommend using the largest dimension of the largest tumor in estimation of tumor size for MFMC carcinoma.