Thymus with B lymphocytes in chronic lymphocytic leukaemia

A 67-year-old man with a diagnosis of chronic lymphocytic leukaemia died suddenly following a coronary occlusion. Peripheral blood lymphocytes labelled with fluorescein conjugated polyvalent antisera to immunoglobulin and immunoglobulin G, and failed to label with absorbed antithymocyte serum. At necropsy, a large thymic tumour, and enlarged mediastinal lymph nodes also contained immunoglobulin G bearing B lymphocytes. The paradoxical finding of B lymphocytes with monoclonal surface immunoglobulin in a thymic mass is most unusual in chronic lymphocytic leukaemia.