[Two patients with chronic lymphocytosis of large granular lymphocytes; benign or premalignant?].

In two female patients aged 44 and 86 years, a chronic lymphocytosis was observed caused by a proliferation of large granular lymphocytes (LGL). The first one had been successfully treated for Hodgkin lymphoma long before, the second had diabetes mellitus type 2. Immunophenotyping showed the proliferating lymphocytes to be natural killer (NK) cells. In contrast to the proliferation of B- and T-lymphocytes, data on the prognosis and treatment of NK-lymphocytosis are very scarce. A literature search revealed three major clinical entities in which LGL proliferate: at one end of the spectrum we see the very aggressive NK-LGL leukaemia, at the other, NK-lymphocytosis, a benign chronic disorder, in between is the relatively indolent chronic T-LGL leukaemia. Both patients suffered from chronic NK-lymphocytosis with a favourable course; there were no further symptoms 4 and 2 years, respectively, after the diagnosis. In cases of prolonged lymphocytosis of unknown origin, immunophenotyping of the lymphocytes is essential. Only in this way can one arrive at the proper diagnosis and reach conclusions as to the prognosis and the possible methods of treatment.