Activation of the canonical and noncanonical NF-κB pathways in transformed B cells following B cell receptor engagement by exogenous or endogenous antigens as well as CD40L and BAFF ligation have been considered a central event in the pathogenesis of extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma), at various anatomical sites such as salivary glands, stomach, and ocular adnexa. The gene discussed is CD40LG; the disease is MALT lymphoma.