Macrophages in non-Hodgkin lymphomas and hairy cell leukaemia.

Methods used in the study of human mononuclear phagocytes in vitro were applied to surgical specimens from 49 patients with non-Hodgkin lymphomas and eight patients with hairy cell leukaemia. Two of the tumours (both classified as "true histiocytic" neoplasms by the Kiel criteria) were distinguished by the presence of atypical macrophages in the in vitro system. In one the atypical cells were adherent; in the others they were non-adherent. These tumours were the only examples of mononuclear phagocyte neoplasia identified in this series. All the remaining 47 cases of non-Hodgkin lymphoma were judged to be of lymphoid origin. While initial observations on hairy cell leukaemia-derived spleen cells suggested macrophage neoplasia, this impression does not stand up to more detailed analysis. The findings are more in keeping with a B lymphoid cell lineage. In hairy cell leukaemias and low grade lymphoma the proportion of macrophages per gram weight of tissue is diminished. This suggests a deficiency of macrophage functional activity compared with normal; the nature of this defect is not clear.