An electron microscopic study of central nervous system sarcoidosis.

Although the fine structure of extraneural sarcoidosis is well documented, ultrastructural study of central nervous system (CNS) sarcoidosis has been limited. Electron microscopic (EM) examination of 3 biopsy cases of CNS sarcoid revealed a mixed cellular population of lymphocytes, epitheloid cells, and multinucleated giant cells. The epitheloid and multinucleated giant cells shared common ultrastructural features of nuclei and cytoplasm. In addition, they displayed similar specializations of the cell surface, including subplasmalemmal linear densities (SLD) and villous projections. These findings recapitulate those described in extraneural sarcoidosis and other granulomatous disorders. This supports the contention that the macrophages or epitheloid cells present in CNS lesions are derived from the same mononuclear phagocytic system as their systemic counterparts.