Cerebral granular cell tumor.

Intracerebral granular cell tumors (GCTs) are a rare finding. We report here on a case of cerebral GCT in a 47-year-old man who suffered with severe headache. The tumor appeared as a relatively well-defined, enhancing mass at the periventricular white matter of the left occipital lobe of the brain. Histologically, the tumor was entirely composed of granular cells. Some of the tumor cells showed peripherally accentuated cytoplasmic granules with central clearing, which produced a unique "targetoid" appearance. The granular cells of the current case were positive for neuron-specific enolase (NSE), S-100 protein, GFAP, vimentin, CD 68, lysozyme, and alpha-1-antitrypsin. These wide immunoexpressions were not observed for the previously reported cerebral GCTs. Interestingly, this case showed "targetoid" or "reversed targetoid" immunoreactive patterns in NSE, CD68, GFAP, and vimentin. Despite these wide immunoexpressions and the lack of any association with astrocytoma, the histogenesis of cerebral GCTs is still suggested to be of a glial origin, based on the tumor location, the GFAP positivity and the ultrastructural findings, of which the latter showed intermediate filaments, and these are reminiscent of neoplastic astrocytes.