The lower discordance rate found in our study is unlikely due to the representation of patients who had early-stage disease without evidence of metastatic disease because of possible independent modes of dissemination through the hematogenous and lymphatic routes 35 The rates of HER2 protein overexpression in DTCs ranged from 21% to 60% in previous studies of patients with operable breast cancer. The gene discussed is ERBB2; the disease is breast carcinoma.