Reactive histiocytosis in acute lymphoblastic leukemia and non-Hodgkin's lymphoma.

An extensive hemophagocytic syndrome in the termination of one case of pre-T acute lymphoblastic leukemia (ALL) and another case of non-Hodgkin's lymphoma (NHL), are described. Since most of the proliferating cells were mature macrophages and these cells were limited in the mononuclear phagocytic system (MPS), it was determined to be a reactive histiocytosis rather than histiocytic medullary reticulosis (HMR) or malignant histiocytosis (MH). The pathogenesis of the HMR or MH-like syndrome in these patients is discussed, and it is considered that this might be a reaction of the bacterial sepsis related to their immunosuppressed state secondary to the pre-existing malignancies and/or the cytotoxic therapy. The literature was reviewed. Based on a proposal for differential diagnosis between reactive histiocytosis and MH (or HMR), the heterogeneity of HMR-like syndrome complicating the malignancies are clarified.