Monocytes in body fluids appear as they do in peripheral blood. Cytocentrifugation may exaggerate the vacuoles or make the cells appear larger.

Macrophages are larger than monocytes and about the same size as mesothelial cells. Their cytoplasm often contains numerous vacuoles.

Erythrophages are macrophages with engulfed red blood cells.

These cells can be seen after hemorrhage. They may also just be the result of the macrophage continuing phagocytic in vitro activity after collection.

Lipophages are macrophages with abundant lipid vacuoles. These vacuoles may be full of extracellular lipids or the remnants of cell membranes. They may appear in CSF following a brain infarct.

Siderophages are macrophages with coarse dark blue hemosiderin granules.

They can be seen even months after hemorrhage as macrophages phagocytose the hemoglobin remains of red blood cells.

They may also be seen in disorders where there is excessive iron buildup.

Macrophage has the appearance of a “signet ring” with several vacuoles forming what looks like the finger hole of a ring. The nucleus is pushed to one side of the cell, giving its distinctive appearance. Note that this type of macrophage is different from a true signet ring cell.

May also be seen in disorders where there is excessive iron buildup.

Mesothelial cells have a wide variety of morphologies. They are about the same size as macrophages, so they can be confusing. Macrophages can usually be differentiated by the presence of vacuoles and a lacey chromatin. If both cell types are present and differentiation is difficult, take a look around the slide to get an idea of each kind of morphology before starting a differential.