These are bipolar microglia with rod-shaped nuclei that appear as a result of tissue damage, e.g., encephalitis. Microglia also contain aggregates of small nodules called glial nodules.
Macrophages are cells mobilized to digest lipids, the main constituent of myelin sheaths, as a result of tissue damage from various causes. They are generally derived from serum monocytes. Englobed lipids have been found within cells by lipid staining and are therefore also called lipid phagocytes or fat granule cells. In contrast, when hemorrhage-induced tissue deposits of iron components such as hemosiderin are englobed, they are referred to as hemosiderin-laden macrophages or iron granule cells.
Macrophages are known to englobe debris surrounding destroyed neurons. This phenomenon is called neuronophagia. It is often observed in neuronal degeneration within the motor cortex in inflammatory lesions as well as in ALS.
In AIDS leukoencephalopathy, a brain lesion directly caused by AIDS infection, macrophages affected with the AIDS virus appear as multinucleated giant cells.
In globoid cell leukodystrophy, multinucleated giant cells that englobe abnormal metabolic products are called globoid cells.