This mutation characterizes about 30% of Activated Diffuse Large B Cell Lymphomas (ABC-DLBCL), 52% of IgM monoclonal gammopathies (IgM-MGUS), 54% of the cutaneous DLBCL, 70% of primary DLBCL involving the central nervous system, and 90% of MW, while is absent in IgM multiple myeloma (MM) [87]. The gene discussed is CD40LG; the disease is monoclonal gammopathy.