Our aims were (1) to unveil a possible lateralization with regard to HER2 expression, lymph node involvement, or molecular subtypes of breast cancer, (2) to examine left–right asymmetries with respect to angiogenic, hemostatic, and inflammatory mediators in patients with primary, invasive breast cancer, and (3) to explore whether the tumor laterality can predict disease recurrence. The gene discussed is ERBB2; the disease is breast carcinoma.