Increase or decrease from surgery to the onset of adjuvant chemotherapy was independent of tumor size but, surprisingly, significantly more increases occurred in N0 patients (15/30) vs. N1 patients (4/24) (p = 0.011), in hormone receptor-negative patients (7/10) vs. hormone receptor-positive patients (14/43) (p = 0.029), in HER2/neu− (15/29) vs. HER2/neu+ (3/17) (p = 0.022), and patients with initially low numbers (below 2500/mL) of circulating cells suspected to be of tumor origin (13/18) vs. initially high numbers (10/36) (p = 0.002). The gene discussed is ERBB2; the disease is neoplasm.