The monocytic cells seen in body fluids have variable morphology as they have the ability to transform into phagocytic macrophages. Since there is a continuum of morphologic forms during this transformation, some laboratories combine these cells into a single category called monomacrophages. The function of a monocyte or macrophage is to remove and recycle dead or dying cells so they do not become body irritants.
Macrophages (see arrows in the image on the right) are generally larger than typical monocytes. Macrophages contain more cytoplasm, which is frequently heavily vacuolated. The nucleus tends to be pushed to the edge of the cell and the cytoplasm may have ingested materials present. You may see ingested RBCs or WBCs, lipid droplets, hemosiderin, and even ingested crystals. Hemophagocytosis is phagocytosis by macrophages of erythrocytes, leukocytes, platelets, and their precursors. The monomacrophage may also be identified by the cell or particle phagocytized. Examples of these cells are:
- Erythrophage - monomacrophage containing red blood cells
- Neutrophage - monomacrophage containing neutrophils
- Lipophage - monomacrophage containing lipid particles
- Siderophage - monomacrophage containing hemosiderin particles
