Anti-IL-6 monoclonal therapy was recently approved by the Food and Drug Administration for patients with Castleman disease.41 In the context of solid tumors, despite success in preclinical studies,41 the efficacy of such treatment was limited in Phase I–II clinical trials among patients with prostate, ovarian, and lung cancers.46 47 Our results further support these clinical studies, because we demonstrated that anti-IL-6 treatment does not inhibit primary tumor growth, whereas it dramatically reduces metastatic burden. The gene discussed is IL6; the disease is Castleman disease.