As MALT lymphoma derives from postgerminal centre memory B cells, it is not surprising that plasmacytic differentiation may occur in up to 30% of extragastric MALT lymphomas and is very often associated with serum paraproteinaemia.89 Histologically, small groups or sheets of light chain restricted lymphoplasmacytoid cells and/or plasma cells, usually containing IgM, are part of the infiltrate, occasionally showing intranuclear periodic acid–Schiff-positive material (Dutcher bodies). The gene discussed is CD40LG; the disease is MALT lymphoma.