Some laboratory professionals may attempt to make a distinction between monocytes and macrophages. Macrophages are the phagocytes that originate from monocytes. However, it is not necessary to morphologically distinguish these cells. The transformed monocyte/macrophage appears when clean up of the CSF is necessary because of degenerating cells and debris, often due to a subarachnoid hemorrhage (SAH) or meningitis. In this image, one monocyte and two macrophages are indicated by the arrows, although it is not necessary to report them as distinct cells. Note the lacy appearance of the chromatin and the appearance of nucleoli in the macrophages. The nucleus of the monocyte is kidney bean- or horseshoe-shaped. The nucleus may also be round or oval.