Significance of lymphocytosis in adults.

11/19 adults with a persistent increase in the total lymphocyte count, but with neither lymphodenopathy, hepatomegaly, nor splenomegaly, proved to have a monoclonal increase in B lymphocytes indicative of chronic lymphatic leukaemia (CLL). All remaining 8 patients had increased numbers of T-lymphocytes, more often of the helper than of the suppressor subsets. All the patients with a lymphocyte count in excess of 10 000/microliter, but only 5/13 patients with a lymphocyte count below 10 000/microliter had CLL. In adults a sustained lymphocytosis is thus not an adequate basis for the diagnosis of early CLL, which requires the demonstration of a monoclonal population. The T-lymphocytosis is likely to be reactive rather than neoplastic in nature.