Infiltrative astrocytomas with granular cell features (granular cell astrocytomas): a study of histopathologic features, grading, and outcome.

Granular cell astrocytomas (GCAs) are rare, incompletely characterized infiltrative gliomas that contain a prominent component of granular cells. Such tumors can readily be mistaken for reactive conditions. We studied 22 cases to explore their morphologic spectrum, establish features useful in distinguishing GCA from nonneoplastic diseases, and to determine which parameters correlate with biologic behavior. Tumors occurred in 17 men and five women, ranging in age from 29 to 75 years, who presented mainly with seizures, headache, aphasia, or hemiparesis. Radiologically, high-grade GCAs were contrast-enhancing, cerebral hemispheric masses with prominent peritumoral edema. All contained sheets or interspersed large, round cells packed with eosinophilic, PAS-positive granules. Lymphocytic infiltrates, either perivascular or admixed with neoplastic cells, were present in 14 tumors. Transition to typical infiltrating astrocytoma was noted in 16 cases; of these, granular cells comprised 30-95% of cells. Six tumors consisted almost entirely of atypical granular cells. By WHO criteria, four GCA were grade 2, seven were grade 3, and 11 were grade 4. Glial fibrillary acidic protein staining was seen in all but one tumor, and the majority were immunoreactive for S-100 protein, KP-1, ubiquitin, and epithelial membrane antigen. Although MIB-1 proliferation indices increased with tumor grade, granular cells accounted for only a minority of immunoreactive cells. Among 18 cases with follow-up, 15 recurred after surgery and resulted in death (mean survival, 7.6 months). Two patients died postoperatively, and one was alive at 51 months. Granular cell astrocytoma is an uncommon morphologic variant that appears to be rapidly progressive and usually fatal.