Neoplasms of the mononuclear phagocyte system: criteria for diagnosis.

The Mononuclear Phagocyte System, including promonocytes, monocytes, and tissue histiocytes (macrophages), gives rise to moncytic leukaemias and histiocytoses. A classification of these neoplasms by their presumed cell of origin is proposed, and criteria for their diagnosis are given. Histopathological, cytochemical, immunological and ultrastructural features useful in distinguishing these disorders form other haematopoietic or lymphoid neoplasms are presented in detail. The resulting classification reflects our knowledge at this time; as techniques become available to define further functional subpopulations of mononuclear phagocytes, it is likely that this classification will become as diverse as that of lymphoid neoplasms.