MZBCL proliferation depends on constitutive NF-κB signaling provoked either by combined CD40/BCR/TLR9 signaling or by the API2-MALT1 fusion protein. Gastric- and salivary gland MZBCL, lacking t(11;18), depend on CD40L and other T-help factors, together with the (RF-specific) BCR and/or TLR7/9 NF-κB signals. MZBCL with constitutive NF-κB signaling due to t(11;18), do not depend on T-helper factors, BCR nor TLR signaling.