A study by Petit et al. that included patients with marginal zone B-cell lymphomas and lymphoplasmacytic lymphomas showed that the absence of expression of both Ki-67 and interferon regulatory factor 4 (IRF4 or multiple myeloma oncogene-1-protein, MUM1), were associated with better prognosis [21]. The gene discussed is IRF4; the disease is lymphoplasmacytic lymphoma.