THE ASCENT and decline of concepts surrounding the cells known as histiocytes have been periodic phenomena for many years. Shortly after 1900, such elements were described under the rubric of "clasmatocytes" with the contention that they derived from peripheral blood leukocytes and emigrated from the bloodstream into tissue sites. Others likewise regarded them as "primitive wandering cells." In contrast, in their well-known and then-standard A Textbook of Pathology (first published in 1908), Beattie and Dickson1 offered the opinion that "histiohematogenous cells" were actually endothelial in character and originated from the lining cells of blood vessels and lymphatics. Sigal et al2 reported that Metchnikoff was the first to use the term macrophages in reference to the cells in question, in recognition that they were large (macro) cells that had the capacity to engulf (phagocytose) other cells, cellular debris, microorganisms, and foreign materials. He proposed that they were synonymous with "fixed tissue histiocytes" and felt that they were related to the latter in a functional schema, the macrophage system. Furthermore, Metchnikoff's construction was regarded as identical to the reticuloendothelial system, a term that had been coined in deference to the theory elucidated by Beattie and Dickson and others.
Wick MR, Patterson JW. Cytophagic Histiocytic Panniculitis—a Critical Reappraisal. Arch Dermatol. 2000;136(7):922-924. doi:10.1001/archderm.136.7.922