Cytological and functional characterization of three cases of malignant histiocytosis

This report is a cytological and functional description of 3 cases of malignant histiocytosis (MH). These patients suffered from an intense proliferation of histiocytic cells that occurred predominantly in the bone marrow in 2 cases (the primitive cell type of MH), and in the spleen, liver and intraabdominal nodes in the third patient (the mature cell type of MH). The malignant cells carried the cytological markers typical for the monocyte-macrophage series, e.g., acid phosphatase, NaF-sensitive naphthol-AS-acetate esterase, acid alpha-naphthyl-acetate esterase, lysozyme, and also Fc-IgG-receptors and mouse C3-receptors. Their in vivo phagocytic activity was investigated by ultrastructural studies. In every case, the histiocytic cells phagocytosed Candida albicans in vitro. The proliferative histiocyte compartment differed from that of the mature cells, although these two cell compartments were morphologically indistinguishable in the primitive-cell-type cases of MH. Malignant histiocytes were capable of destroying phagocytosed fungi, but this ability was clearly inferior to that of the mature histiocytes in these 2 cases. The results revealed that most, if not all, monocyte-macrophage characteristics are present in the malignant cells in MH. Nevertheless, the morphological and clinical features seemed to be variable.