Benign Histiocytic and Dendritic Cell Disorders

Histiocytes and dendritic cells (DCs) play critical roles in tissue homeostasis and immunity. DCs are derivative of the hematopoietic stem cell lineage, whereas histiocyte is a morphological term that is used to delineate tissue macrophages and sometimes encompasses both macrophages and DCs. Morphologically, we can easily distinguish between DCs (stellate in shape, with numerous cytoplastic projections) and macrophages (large, containing abundant foamy cytoplasm, with engulfed dusty granules). Mature DCs appear to have a larger surface area than the immature forms because of their longer cytoplasmic projections. DCs and macrophages have separate functions. Benign dendritic and histiocytic cell disorders comprise a heterogenous group of reactive, polyclonal proliferations with diverse etiopathogenesis. Apart from hemophagocytic lymphohistiocytosis (HLH), these conditions typically do not necessitate therapy. It is crucial to differentiate these disorders from malignant dendritic cell and histiocytic diseases.