Lymphocytes within glial cells ("emperipolesis") in a case of a granular cell tumor.

A case of a combined neurofibroma - granular cell tumor of the left middle cranial fossa with infiltration of the temporal lobe and expansion into the orbit is presented. The granular cell tumor shows big fibrillary astrocytes in its peripheral zone. Even in the tumor-free brain tissue adjacent to the tumor plenty of these obviously reactively proliferated astrocytes are found. Furthermore, lymphocytes within the cytoplasm of such astrocytes ("emperipolesis") strike the eye. Neither the lymphocytes nor the astrocytes show signs of damage. A review of the literature and the theories concerning the phenomenon of emperipolesis are given. The problem of its biological significance and the question whether emperipolesis is the result of invasion of engulfment must remain unsolved.