Anaplastic astrocytoma with granular cell differentiation: case report and review of the literature.

In contrast to the relatively common soft tissue form of granular cell tumor (GCT), intercerebral GCTs are rare neoplasms. The Schwann cell is the accepted cell of origin for soft tissue GCTs. However, the origin of intracerebral tumors is controversial. We report a case of a GCT intimately associated with an anaplastic astrocytoma. Immunohistochemical staining with glial fibrillary acidic protein demonstrated focal positive staining within the granular cells. Six GCTs from other body sites were stained with glial fibrillary acidic protein for comparison and all were negative. The granular cell component was diffusely positive for S-100 and negative for epithelial membrane antigen and cytokeratin. Ultrastructurally, filaments characteristic of astrocytic cells were demonstrated within some granular cells. Based on our light microscopic, electron microscopic, and immunohistochemical findings, the granular cell component of this anaplastic astrocytoma is likely astrocytic in origin. We propose that these tumors be designated astrocytic neoplasms with granular cell differentiation and their prognoses dictated by the grade of the glial component.